Genica's MPTrip is the first commercially available portable CD player that can also play recordable CDs filled with MP3 files, and it lists for only $115. The MPTrip's ability to read and decode music stored as MP3 files means that you can squeeze roughly 11 hours of music on one CD, and make it portable. And since I like to have lots of selections with me, I'm already in the habit of carrying around a plastic CD pouch that compacts 40 CDs without jewel cases. Do the math and that translates into an astonishing 400 CDs or 440 hours of music.
Maybe you haven't noticed, but portable CD players have gotten really cheap. Many of the players in Aiwa's top-rated line list for less than $100, and cheap-o players can run less than $40 if you find the right site or store. But for a few extra dollars there's a better portable CD player that will increase the number of songs you can carry tenfold.