Offenhauser [OFF]
No web site listed
Intake manifolds

Ohlins [OHL]
http://www.ohlins.com/
Racing shocks and related components

Oliver Racing Parts [OLV]
http://www.oliver-rods.com/
Connecting rods

Optima Batteries [OPT]
http://www.optimabatteries.com/
Racing batteries

Out-Pace Racing Products [OPP]
www.out-pace.com/
Greasable End Rods

Outerwears [OUT]
http://www.outerwearsracing.com/
Air filter covers

Outlaw Racing Brakes [ORB]
http://www.outlawdiscbrakes.com/
Brake components

Oval Craft [OVC]
http://www.ovalcraft.com/
Aluminum racing seats and racing products