Bimmerforums.com - The Ultimate BMW Forum
Ben Liaw's Big Links Page - The biggest BMW link source out there
bimmerfest.com - General BMW forum
bimmers.com - Home of the E30 M3 SIG
Anthony's E30 M3 Ecke
BMW Car Club of America
BMWsport.net - over 1,200 pictures, BMW Racing Press Releases, a Need for Speed:  High Stakes Section, and more...
E46Fanatics.com - E46 specific site/forum
E90Fanatics.com - E90 specific site/forum
Importation/Federalization Page - Info on getting a Euro car into the country
BMW VIN Decoder - View the model and options of a car by entering VIN

BBS - Quality lightweight street and race wheels
Indocil Art - Custom helmet paint
Larini Systems - High-end exhaust manufacturer
Performance Friction - Performance brake pads, rotors, and racing brake kits
Powerflex - Urethane performance suspension bushings

BMW CA
BMW USA

Motorsports Imaging - Jimmy Sykes' race photos
Olsonimages.com - Showcase for the motorsports photographer Elliot Olson
Speed Arena - Pictures from all types of road racing

Speed World Challenge 
SCCA
NASA
Spec E30
ImprovedTouring.com
BMW CCA Club Racing
trackschedule.com - Listing of driver's school events in the Eastern US
North American Motorsports - Tons of track information