Yeah I have one… only messed with it a little…
You’ll need the following to make it useful, Powered USB Hub, Keyboard, Mouse, 2GB+ SD Card and USB WiFi Adapter, maybe a case as well.
Works great with Raspbmc as a media player, you can install various linux distros and use like a standard pc, if not slow tho. I’ve used mine as a VPN Server to connect into my home network from outside.
On a side note, maybe look at an Arduino. It can be programmed from PC or Mac and will give a basic insight into programming but allow you to visually do something like light LEDs, drive motors, receive switch inputs etc…