iPod car stereo integration is great. You can control your music library with your car stereo's controls. In some cases, you can see track info like artist, song and album information. Best of all, your iPhone's charging via a dock connector while all of this is happening -- that is, if you have a fairly recent integration kit.
While many older car stereo integration kits can play and control music through their iPods and iPhones, they've lost the ability to charge newer models. The reason for this is that Apple re-engineered the dock connector for the iPhone 3G, second generation iPod touch and fourth generation iPod nano onward.
However, you can empower yourself against this annoyance with Scosche's passPORT. The passPORT is a dongle that serves as an intermediary between your car's dock connector cable and your iPhone, charging it while you're enjoying your music.
Scosche has a list on its site with car compatibility information. While my car's kit -- the original iPodYourBMW factory kit -- isn't on the list, it worked flawlessly with the passPORT.
The Scosche passPORT is available at the Apple online store, and at some Apple retail stores for US$19.95.