So, I bought a little organ off eBay for £21. Here's a link:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&rd=1&item=190148255427&ssPageName=STRK:MEWA:IT&ih=009Basically it works by having a fan that blows air across reeds. When you press a key, it lets air pass across the corresponding reed. It's kinda like an accordion, but with the fan instead of bellows. It's got a three octave keyboard and 3 lots of chord buttons for Bb, F, C, G, D, A (one row of minor, one of major and one of bass notes).
I've attached a quick little recording I did (twas just done with sound recorder, so it's not great quality).