As well as the less frivolous things I make, I have also made some more useful, serious things.
Eternity was my undergraduate 3rd year research project. Eternity was a network conceived by Ross Anderson, its purpose to store data on a distributed network such that the data would always be accessible. Even if parts of the networked got cut off or impounded by the authorities, the data would still survive. To offset the risk of getting the NSA on your case, Anderson proposed a payment system linked to storage.
I designed and implemented such a network in Java, and on a small scale it worked, sort of, and I did some very basic analysis and testing on its durability. You can find more about it in my BA dissertation (PDF, 205k), which got me my best mark in my BA finals. If you want to know more then drop me a line.