Via Instapundit, here's a nice review of an FM transmitter that'll let you listen to your music on the car radio. Looks like a great tool for musicians. I often listen to new music for upcoming gigs, reviews, etc. in the car. This will avoid the time/expense of burning a CDR for the car. You can play tracks off of USB stick, SD card, or straight off of your iPod/iPhone etc.
This one gets excellent reviews and it's cheap!
Amazon has it here: