We're using NASCAR.com this year, actually. Recommended by a friend, who is one-half of MRN's fantasy podcast.
League: EDSBS Fantasy Racin'
Unlike Yahoo, which limits drivers to X number of starts per season, NASCAR.com's is a salary cap-style league. Which is much more interesting. I think ESPN uses this too but I generally dislike ESPN's format.
It's not quite up to date with all the drivers' current details (Mark Martin and Juan Pablo Montoya are still available and some drivers have last year's numbers), but it should be by the 500.