How can I burn a CD with folders containing MP3's to listen to in a car? I have a bunch of podcats that I've downloaded as mp3's. I'd like to burn them to a CD in a single directory, call it "podcasts-1". Next week when I download more I'd like to add them to the CD (if there's space) in a directory called "podcasts-2".

I used to do this on a Windows box using DeepBurner. It super simple but for some reason I've had no luck on my new Macbook Pro. I tried creating a "new image from folder" using the Disk Utility application but that didn't play in the car.
You should use iTunes to burn the MP3 CDs. If I remember correctly, MP3 CDs are very slightly more complicated than just a folder on MP3s on a CD. iTunes does an excellent job. I've also had luck with LiquidCD.