If you follow NASCAR, check out NASCAR Live over in the Windows Phone Marketplace. The lays out everything NASCAR rather nicely on your Windows Phone with pages for News, Races, Rankings, Videos, and a page with links to NASCAR, Driver and Truck (team) Tweets.
Additional features for NASCAR Live include:
Live race details for both NASCAR Sprint Cup and Nationwide tours
Ability to create a secondary tile for any race
Detail list of upcoming races
Detailed driver information.
Completed races will display the final positions for the drivers. The only thing I can think is missing is a map of each track that NASCAR races on and maybe live broadcasts (that may be asking for too much though). Otherwise, NASCAR Live is a fairly comprehensive application for your Windows Phone.
NASCAR Live is a free, ad-supported app that you can find here at the Windows Phone Marketplace.