I spent the weekend in Alexandra Palace (only ten minutes away from me by train) at Hack Day London 2007 (except when I was in church), doing a hardware hack in a team with Ewan Spence and Greg McCarroll.
I intended to spend some time building a personal project, but when Ewan wandered over and suggested rocketry, I switched over like a shot :-). Our project was called Beagle 3; the initial plan was a multi-stage rocket using air/water for the first stage and Diet Coke/Mentos for the second stage, with a camera payload, but our experiments with the Coke, while highly amusing to all the assembled geeks Ewan had called out to watch, didn’t actually result in anything leaving the ground. We had to settle for something a little more modest. I have a web page which gives some details.
To enter the contest, the rule was that you had to use either a Yahoo or a BBC API. We, in fact, used every single Yahoo API – by loading them onto a USB key and firing it up on top of the rocket :-) For this, we got a prize for “Best Hack of the Rules”.