Watching the Pocono 500, I loaded up NASCAR.com and TNT RaceBuddy. You can attached your MySpace, Twitter and Facebook accounts and update your status in-race. I like what they did. Unfortunately, there's so many status updates (too many fans) that it looks like a bunch of noice and zero conversation.
http://www.tnt.tv/sports/nascar/racebuddy09_live/?o_cid=rbc18
Update: RaceBuddy hung up on my on my 2nd update :(