Personal Web sites devoted to CPR:
There are setups, a FAQ, and some excellent essays giving advice on racing in general and in CPR in particular at the Apex. Carsets are available from Devin Pruzin at Jim Getzin's site and from the Redwolf30 site, and Jim also has race setups available. The US Pits has some good frame rate tips and other info.
Also, if you have either the full or demo version of CPR, you can race with other people at Microsoft's Internet Gaming Zone.