There is a ton of stuff available for racing simulations on the Web. Below are links to Web sites and Usenet newsgroups with more information and enhancements for varioius racing simulations.
For ICR2, I especially like Shane Pitkin's ICR2 setups available from Velocity Motorsports, which are excellent for learning the tracks and can be adapted to use as race setups. Sim Cyberworld has an excellent collection of setups and hotlaps, as well as carsets.
I highly recommend the ICR2 sound enhancement and carsets available from The Sim Project, which has just released beta versions of 3D-enhanced tracks for Rendition-ready ICR2. Also at The Sim Project are enhanced AI files for many of the tracks, including the brilliant Mid-Ohio AI by David Mocnay.
Be sure you check Snake Racing for Jake Myers' latest setups. Jake Myers is one of the hottest drivers on the Web, and his setups could be the fastest setups available anywhere.
Several of these sites support online and offline racing series, and offer a variety of utilities for use with ICR2 and other sims. Also try Sim Racing News, which, though it hasn't been updated in a while, has sim-related information, such as reviews, hot laps and replays, track guides, and links to still other sites. Also, please check out my more detailed reviews of racing sims at Thunder Valley Racing.
If you have access to Usenet newsgroups, check out rec.autos.simulators for the latest scoop and lots of technical help as well as a variety of opinions. If you have CompuServe access, try the MODEMGAMES and SPRTSIMS forums for online and offline racing series and modem play. And finally, try The Games Domain for demos and reviews of many sims. If the main site in the UK is slow, I suggest you try the site in Russia.