Motorsports
Don's DIY Den - http://www.diyden.net/
Guides on how to create go-kart, off road buggies and mini bikes and features reviews of already built models.
Driver Database - http://www.driverdb.com/
Auto racing and kart drivers database. Has an extensive list and information on some 30,000 drivers.
Indycarscene.com - http://indycarscene.com/
A discussion forum that focuses on Indianapolis Autos. Includes links to other resources.