I've been tempted to make a little electronic boom box for my Mom. Just a box similar to the stereos in cars that play MP3s with FAT32 USB drives. Then I would put her favorite music on various drives that she could plug in whenever she wanted. Make sure it has some nice speakers on it and an Aux jack.

Edit: Also a must have is some faux wood grain!

The interface will just be a standard play pause stop skip rewind with big fat buttons. Preferably the most satisfying ones I can find on Mouser. Nice and clicky.

Cassette tapes are cool, but they are a pain. I still remember the horror of hearing my walk man turn my Top Gun Soundtrack cassette into plastic waste. Never again!