This add-on for the Nintendo DS not only lets you play MP3 files, but it lets you run tons of homebrew games on the portable console.
Datel’s Games ‘n’ Music plugs into the DS and gives you an easy way to play custom games and apps on the DS and DS Lite. The $30 add-on even comes with a CD loaded with 25 mini-games to get you started. It also bundles a video converter that makes it easy to transfer media clips to your DS too (there’s a bundled USB cable to make transfers painless.) While it only comes with 128MB of storage, it’s expandable up to 2GB thanks to a Micro SD slot.
Available from TotalConsole, the Games ‘n’ Music costs $29.99.