There's a couple of forums I frequent on the Internets...............
~~NewsOnF1.com.............
www.newsonf1.com
I'm probably here the most as I am a forum moderator here(my bailiwick is North American Motorsports, in particular the two major open wheel series in the U.S., the Indy Racing League(
www.indycar.com ) and the Champ Car World Series (
www.champcarworldseries.com ); I've been a regular poster there since June 2005(just look for the screen name mlittle)
.....remind me to mention sometime how I got to be a moderator there....... It's main focus, as the name suggests, is the "Pinnacle of World Motorsport", Formula 1, but there are forum sections for the Australian V8 Supercars, NA Motorsports, MotoGP and other areas as well(a Lounge area, a Motorsport area for every other form of racing, a Trivia section, etc.). Its' a really cool site; check it out when you get the chance!
~~AutoRacing1..................
www.autoracing1.com
Another great autoracing site; its' a pay-subcription site, but it is worth the small chunk of change for some of the most up-to-date news/rumors in motorsports; other than the sometimes vitriolic
anti-IRL, anti-NASCAR and anti-GrandAm views expressed here and on their motorsports forum, its' still a great site
~~Speed Channel................
www.speedtv.com
Another interesting motorsports site; they cover pretty much everything; there's also an interesting meesage board there as well
Other sites of interest.................................
Formula 1............................................
www.formula1.com
Grand Am............................................
www.grand-am.com
American LeMans Series......................
www.americanlemans.com
Atlantic Championship.........................
www.champcaratlantic.com