Create a USB device that lets you retrieve CDs/DVDs at the click of a mouse instead of digging through your room, shelves, storage bins, etc only to find an empty case. Am I right?
You could buy a Sony Disc Changer from Amazon for less than $300. ThinkGeek.com sells one for less than $120. But making one from scratch? That's priceless! Not to mention cool and useful.
Bonus points if the carousel has an integrated optical drive so it actually plays the disc, too. Oh yeah.
http://www.amazon.com/Sony-DVPCX995V-400-Disc-Changer-Player/dp/B000A3XRSO