Wow, I really envy you guys who found some free power! In Denmark, the kWh rate is about 0.36 USD, so it's pretty expensive to mine over here, haha.

I turned out to have a Radeon 5850/Core i5-750 SFF PC lying around, so that's been setup for mining. Definitely going to upgrade this though: removing the (albeit well cooled) SFF case, and buying more GPU's. (Too bad those PCI-E riser cables seem so.. rare?)

There seems to be a lot of hype around the Radeon 7950, but man, that card is just insanely expensive. Over here, a used 5850 is around 1/4th the price - and maybe I'm just lucky, but they seem rather easy to get hold of as well.