Just about every serious JDM Tuning Garage or Parts manufacturer listed as well as many USDM Manufacturers in no particular order.  Created by John Bruno and John Pruner:

ACT - http://www.advancedclutch.com
5Zigen - http://www.5zigen.co.jp
Abflug - http://www.ab-flug.co.jp
Advan - http://www.advan.com
AEM - http://www.aempower.com
Aeroquip - http://www.aeroquip.com
Arospeed - http://www.arospeed.com
Alles Create - http://www.alles-create.co.jp
Apex Integration - http://www.apexi.com
Autometer - http://www.autometer.com
B&M - http://www.bmracing.com
Blitz - http://www.blitz.co.jp
Bomex - http://www.bomexaero.com
Border - http://www.border-racing.com
Bosch - http://www.boschusa.com
Bozz Speed - http://www.bozz.co.jp
Brembo - http://www.brembo.com
Catz - http://www.fet-us.com
Centerforce - http://www.centerforce.com
Cusco - http://www.cusco.co.jp
C-Westin - http://www.c-west.co.jp
DC Sports - http://www.dcsports.com
Defi - http://www.nippon-seiki.co.jp/defi/
Denso - http://www.denso.co.jp
East Bear - http://www.east-bear.co.jp
EBC Brakes - http://www.ebc-brakes.com
Eibach - http://www.eibach.com
Electromotive - http://www.electromotive-inc.com
Energy Suspension - http://www.energysuspension.com
Enkei - http://www.enkei.com
Falken - http://www.falkentire.com
FEED - http://www.pac-gate.co.jp/feed
Fluidyne - http://www.fluidyne.com
GAB - http://www.yrc.co.jp/yfc/gab
Greddy - http://www.greddy.com
H&R - http://www.hrsprings.com
Haltech - http://www.haltech.com.au
Hawk Performance - http://www.hawkbrake.com
HKS - http://www.hksusa.com
JUN - http://www.junusa.com
KAAZ - http://www.kaazusa.com
Knight Sports - http://www.knightsports.co.jp
Koni - http://www.koni-na.com
Koyo - http://www.koyo-rad.co.jp
KYB - http://www.kyb.com
MazdaSpeed - http://www.mazdaspeed.net
Momo - http://www.momo.it
Motec - http://www.motec.com
MSD - http://www.msdignition.com
Neuspeed - http://www.nuespeed.com
NGK - http://www.ngksparkplugs.com
Nology - http://www.nology.com
Omori Gauges - http://www.omorimeter.com
Pace Setter - http://www.pacesetterexhaust.com
PIAA - http://www.piaa.com
Power Slot - http://www.powerslot.com
Project Mu - http://www.project-mu.co.jp
Racing Hart - http://www.rhc.co.za
RE Amemiya - http://www.re-amemiya.co.jp
Recaro - http://www.recaro.com
R-Magic - http://www.rmagic.net
RPS - http://www.turboclutch.com
RUN Racing - http://www.pac-gate.co.jp/run
SARD - http://www.sard.co.jp
Sparco - http://www.sparcousa.com
Speedline - http://www.speedlinecorse.com
Spoon Sports - http://www.spoonsports.co.jp
SX - http://www.essexind.com/sx_frame.htm
Tanabe - http://www.rd-tanabe.com/
TEIN - http://www.tein.co.jp
TODA Racing - http://www.toda-racing.co.jp
Tokico - http://www.tokicogasshocks.com
Tomei - http://www.tomei-p.co.jp
TOMS - http://www.tomsusa.com
TOMS - http://www.tomsracing.co.jp
Unorthodox - http://www.unorthodoxracing.com
VeilSide - www.veilside.co.jp
Volk Racing - http://www.volkracing.co.jp
XS Engineering - http://www.xs-engineering.com
Garage TT- http://plaza26.mbn.or.jp/~GarageTT/
Garage Active- http://www.garage-active.net
Phoenix Power-    http://www.phoenixs.co.jp/bigsite/home.html
Coleman Racing- http://www.colemanracing.com/prodex/
Wilwood- www.wilwood.com
Acre- http://www.acre.co.jp/viens/
Alamo Motorsports- http://www.alamomotorsports.com
back Yard Turbo- http://www.back-yard-productions.com/index.htm
Baker Precision- http://www.bakerprecision.com/setrab1.htm
Biot's- http://www.biot.co.jp/main/top.html
Brash Boy-  http://www.brashboy.net/
Behrent's- www.behrents.com
Pegagsus- http://www.pegasusautoracing.com/
CJ Motorsports- http://www.cj-motorsports.com/
C-One- http://c-one.co.jp/
Crux- http://www.crux-eng.com
Cruise- http://www.cruise-power.co.jp/index.html
Fujitsubo- http://www.fujitsubo.co.jp/mc-prod/
Ganador Park- http://www.ganador.co.jp/index.html
G-Grow- http://www.g-grow.co.jp/
D-Jac- http://www.djac.co.jp/
Techno Pro Spirits- http://www.tp-spirit.co.jp/index.html
Tomei- http://www.tomei-p.co.jp/
Do-Luck- http://www.do-luck.com/
Dog Fight Pro- http://www.dogfightpro.com/
Day Pack Works- http://www.dpw-jp.com/
Esprit Super Tuning- http://www.esprit.to/
Technical Shop Infini- http://www.infini-d.co.jp/
Advance- http://www.advance-jp.com/
Bee racing- http://www.bee-r.com/
Iris garage- http://www.iris.dti.ne.jp/~riki5115/5frameHeadLine.html
J-Blood- http://www.j-blood.com/
Japanese Auto-  http://www.japanese-auto.com/list.html
Kei-Office- http://www.kei-office.co.jp/lineup/suspention.html
KORacing- http://www.koracing.net/products.html
Ludi- http://www.luedi-motorsport.ch/index1.htm
M2- http://www.m2performance.com/
Original Box- http://www.originalbox.co.jp/
P.P. El- http://www.pp-el.com/
PWR- http://www.pwr-performance.com/page867169.htm
Quest- http://www.rcm-quest.co.jp/
Racing Gear Hyper Station- http://www.racinggear.co.jp/frame.html
Silk Road- http://www.silkroad-jp.com/
Swain- http://www.swaintech.com/header.html
T and E (AKA Vertex; yes you can get Vertex IS300 bumpers)- http://www.t-and-e.co.jp/top.html
TD-Craft- http://www5a.biglobe.ne.jp/~td-craft/
TRD Japan Online Catalog-  http://www.toyota-trd.com/
Up garage- http://www.upgarage.com/
Nagisa Auto- http://www.nagisa-auto.com/
Kakimoto-  http://www.kakimotoracing.co.jp/
Art Garage-  http://www.artgarage.co.jp/shop/index.html
Parsec-  http://www.nnet.ne.jp/~rts/
Artist Racing Factory-  http://www.artist-jp.com/
Earl Tec- 4AGE Tuning- http://www4.ocn.ne.jp/~earltec/
I.A. Tec- http://www.iatec.net/
RS Aizawa-  http://www.rsaizawa.co.jp/
RS Aizawa Fukuoka- http://www.f-aizawa.com/
I.Mec- http://www.imec.co.jp/index.htm
I.Feelin' Rotary Specialists- http://www.tsbar.com/ifeelin/
Autostrada- http://members.jcom.home.ne.jp/autostrada-hp/autostrada.html
Axis- http://www.axisworld.co.jp/
Asada Racing- http://www.asada-racing.com/
Ask Sport- http://www.asksport.co.jp/
Technical Shop Advance- http://www.advance5504.com/index.htm
Auto Advance- http://www.autoadvance-inc.co.jp/
Anniversary Racing- http://www.a-rf.co.jp/
Avance- http://www.tim.hi-ho.ne.jp/magic/
Auto Service Avante (One of the Few Z31 Tuners)-  http://www.worldarts.co.jp/avante/
Arita Speed-  http://www.aritaspeed.com/
Ultimate SPL- http://www.ultimate-spl.gr.jp/
Motor Spirit Alpha- http://www.ms-alpha.com/
Rigid- http://home2.highway.ne.jp/rigid/index.html/
Arvou- http://www3.yomogi.or.jp/arvou/arvou.htm
Arrow- http://www.arrowrs.com/
Rally Tech Uncle- http://www.rt-uncle.co.jp/
Technical Shop Infini-  http://www.infini-d.co.jp/
Infini Racing- http://www.infini-r.com/
Pro Shop Iida- http://ps-iida.co.jp/
Yellow Magic-  http://www.yellowmagic.co.jp/
Ikeya Formula- http://www.ikeya-f.co.jp/  (Good S13 Parts)
Rotary Engine Support Garage IRS- http://www.bea.hi-ho.ne.jp/itoushyoukai/
Interceptor-  http://www1.odn.ne.jp/~cal40710/
Integral Kobe-  http://homepage1.nifty.com/integral_kobe/
RE-Wing- http://www.re-wing.co.jp/
Waste Sports-  http://www.waste.co.jp/
UE Mura Motors- http://www.e-uemura.com/
ATS-BM- http://www.ats-bm.com/
Motec Japan- http://www.motec.jp/
Garage HRS- http://www.garagehrs.com/
HKS Kyusyu Tuning- http://www.hks-kyusyu.co.jp/
Expert OZ AE86 Tuning- http://www.din.or.jp/~expertoz/
Executive Racing- http://www.executive-racing.co.jp/
S&S- http://www.sseng.co.jp/
S-Power- http://www.jin.ne.jp/s-power/
Essential- http://www.essential.co.jp/
M"Technic- http://www.ic-net.or.jp/home/mtech/index.html
M's Factory- http://www.ms-factory.co.jp/
Racing Emotion R- http://www.emotion-r.co.jp/
LM Advance- http://www.lm-advance.com/
OTS- http://www.xyj.co.jp/niigata/ots/
ATTKD- http://www.attkd.co.jp/
Auto Service Signal- http://www.as-signal.com/
Auto Signal- http://www.autosignal.co.jp/
Autostaff- http://www.vhp.oricomall.or.jp/hcon/autostaff/
Auto Select- http://www.autoselect.co.jp/
Auto Tech- http://www.auto-tech.jp/
Okada- http://www.okada-eng.com/
Okabe- http://www2.tokai.or.jp/okabejidosha/
Okuyama- http://home4.highway.ne.jp/okuyama/
Kaitaiya- http://www.kaitaiya-r.com/
Kazama- http://www.kazamaauto.co.jp/
Cashiew- http://www.cashiew.co.jp/
Katano- http://www.katano.org/
Kappatsu- http://www.kappatsu.co.jp/
Cart Right- http://www.c-tuneup.com/cartright/
Creative- http://www.creative-sports.com/
Cross Flow- http://www.cfr.jp/top.html
KSP Racing Equipment- http://www.ksp-eng.co.jp/
K Shift- http://www.geocities.co.jp/MotorCity-Pit/8247/k-shift_001.htm
K-Style- http://www.k-style.gr.jp/
K2 racing- http://www.k2racing.com/
KBC- http://www.s-kbc.com/i-mode/i-modetop.htm
Going- http://www.going-jp.com/
Garage Grosshand- http://www1.ocn.ne.jp/~groshand/
Cockpit- http://www.cockpit.gr.jp/
Zeigen- http://www.zeigen-jp.com/
Garage Saurus- http://www.saurus2000.co.jp/
RS Pantera- http://www.rspantera.com/
Summit Racing- http://www.car-promenade.co.jp/summit-racing/index.html
Sansei- http://www.diana.dti.ne.jp/~g-sansei/
Sunyou- http://www.sp-sunyou.co.jp/
Jing- http://www.jing-r.com/
C-West- http://www.c-west.co.jp/index.html
CS-Top- http://www.cs-top.co.jp/
TSGTR- http://www.tsgtr.co.jp/
Signal Auto- http://www.signalauto.co.jp/
Shift Sports- http://www.shift-sp.co.jp/
Syms- http://www.syms.jp/
Jam Racing- http://www.jam-racing.com/
Joule- http://www.joule-su.co.jp/
SuperTechno- http://www.ktpc.or.jp/kp/888888/
RS Start- http://www.rsstart.com/
Start- http://www.start-racing.co.jp/
Sticks Sports- http://www.sticks.co.jp/
Stella- http://www.biwa.ne.jp/~stella/
Speed Corp (Extensive AE86 Parts)- http://www.mctv.ne.jp/~speed_co/
Garage Thrash- http://www.thrash.co.jp/
cecil Sport- http://www5a.biglobe.ne.jp/~cecil-sp/
Zero Sports- http://www.zerosports.co.jp/
Central 20- http://www.central20.co.jp/
Target Racing-  http://target-r.com/
SS Turbo- http://www.ss-turbo.co.jp/
Turbo Shop M- http://www.turboshopm.com
Charge- http://www2.comco.ne.jp/~charge/
Tsukasa- http://www.jp-tsukasa.com/
Tsukasaki- http://www.tsukasaki.co.jp/
T-Get- http://www.t-get.com/
Garage TSA- http://www.garage-tsa.co.jp/
TCS- http://homepage1.nifty.com/tcs/
TD Craft- http://www5a.biglobe.ne.jp/~td-craft/
T-Project- http://www.t-project.ne.jp/page_001.htm
Excel- http://www.excel-sp.com/
Take One- http://www.takeone-web.co.jp/
RS Dino- http://www.rs-dino.com/
Technical Mate- http://www.technicalmate.co.jp/
Techno Pro Spirits- http://www.tp-spirit.co.jp/
Testarossa- http://village.infoweb.ne.jp/~naninani/
Test Run- http://www5a.biglobe.ne.jp/~testrun/
Deck- http://www.deck-japan.co.jp/
Tex Modify- http://www.shibayama-tire.co.jp/tex/
Duke-  http://www.duke-r.com/
Dunamis- http://www.dunamis-r.co.jp/
Dyuvan- http://www.dyuvan.com/
Toda- http://www.toda-racing.co.jp/
Dog Fight Pro- http://www.dogfightpro.com/
Top Secret- http://www.topsecretjpn.com/
Top Fuel- http://www.topfuel.to/
Tommy Kaira- http://www.tommykaira.com/
Trial- http://www.trial.co.jp/takamatsu/
Trust- http://www.trust-power.com/00home/index.html
Dream Factory- http://www.dream-factory.co.jp/
Night Pager- http://night-pager.com/
Nagisa Auto- http://www.nagisa-auto.com/
Newtonland- http://www2.odn.ne.jp/newtonland/
TS Noguchi- http://www.ask.ne.jp/~charmy/tsn/index.html
Hasemi Motorsports- http://www.hasemi-ms.com/
Back Yard- http://www.pac-gate.co.jp/back-yd/
Auto Life Hano- http://www.biwako.ne.jp/~alhano/
Bandoh- http://plaza12.mbn.or.jp/~bandoh/
Power craft- http://www1.ocn.ne.jp/~p-craft/
Big 1- http://www.big1power.co.jp/
Pit Road- http://www.pitroad-ts.com/
AF Hirota- http://www.af-hirota.co.jp/
Fanatic racing- http://www.ab.wakwak.com/~fanatic/
FAM Speed- http://www2u.biglobe.ne.jp/~fam/
Phantom- http://www.phantom-sp.co.jp/
Feast Power- http://www.feast-power.com/
Faith Speed King- http://www.faith-jp.com/
Phenix Auto Center- http://www.phenix-autocenter.co.jp/
Fujimura- http://www.fujimura-auto.co.jp/
Primer garage- http://www.prime-garage.com/
Blackline Racing- http://www.blackline-racing.com/
Prious- http://www.uegaki.co.jp/prious/index.html
Prestage- http://www.gokuraku.ne.jp/prestage/
Prova- http://jprova.co.jp/
Pro Stage- http://www.prostage-jp.com/
Pentroof- http://www.pentroof.co.jp/
Boys Dream- http://www.jade.dti.ne.jp/~b-dream/
RS Horie- http://village.infoweb.ne.jp/~horie/
Bori's Factory- http://www.threeweb.ad.jp/~boris/pctop.htm
Garage Horino- http://www.g-horino.com/
Vortex- http://www7.ocn.ne.jp/~vortex/
Bomber- http://www.garage-bomber.co.jp/
Twincam- http://www.hondatwincam.co.jp/
Mine's- http://mines-wave.com/
Matsuoka- http://www.matsuoka-m.com/
Macchina- http://www.macchina-r.com/
maruha Motors- http://www.maruhamotors.co.jp/
Midori- http://www.midoriseibi.co.jp/
RS Mirai- http://www.cc.rim.or.jp/~k_oku/
Make-Up- http://www.makeup-power.co.jp/
MDRF- http://www5.ocn.ne.jp/~mdrf/
Met's Speed- http://www.mets-speed.co.jp/
Maintenance Garage-http://www2.ocn.ne.jp/~ttf7001/
Kochi- http://www.kochi-f.co.jp/motojima/
Auto Service Mori- http://www.as-mori.co.jp/
Yashio factory- http://www.yashiofactory.co.jp/
Yashiro- http://ccn.aitai.ne.jp/~engineer/
Yours Sports (FC Stuff)-  http://homepage2.nifty.com/yourssports/
Uras- http://www.uras.co.jp/
Garage Rise Up- http://www.garage-riseup.co.jp/index.html
Luck- http://www.luck.co.jp/
Radical Factory- http://homepage2.nifty.com/radical/index.htm
Amkread- http://www.amkread.co.jp/
Reaction Racing (Rotary)- http://www.reaction-racing.com/
Ricoh- http://www.ricohracing.com/
Revolver (AE86)-  http://www.revolver-jp.co.jp/
Auto Mode Limit-  http://www1-1.kcn.ne.jp/%7Elimit/index.html
Laile- http://www.laile.co.jp/
Revolfe (Lexus/Supra) - http://www.revolfe.com/
Reimax- http://www.reimax.com/
Revolution- http://www.revo-tune.com/
Revyou- http://www.revyou.com/
Power Enterprise- http://www.power-enterprise.co.jp/
Grand Slam- http://www.grandslam.ne.jp/gs_top_t.html
Auto Modify Taku- http://www.taku-r.com/
Junction Produce VIP Tuning- http://www.junction-produce.co.jp/
Evolution VIP Tuning- http://www.evolution.co.jp/
Varis- http://www.varis.co.jp/
Mid Power- http://midpower-web.hp.infoseek.co.jp/info_2.htm
Club 3SG- http://www.din.or.jp/~twincam/
Koma Koma- http://komaj.hp.infoseek.co.jp/
Mid yadayada.com- http://www.geocities.co.jp/HeartLand-Asagao/2840/


-John Pruner
redvalkyrie