I bought a popup tent on ebay, and it arrived this lunchtime. You take it out of the bag and throw it in the air, and hey presto! A tent!

Putting it back in the bag is slightly less hey presto, but it only took me about 5 minutes, so that isn't too bad.

Also it has a round backpack thing that makes you look like a Mutant Ninja Turtle. Hurray!