Don't try this one if you have a life (if you're like me, then it's okay...)
After an in-class discussion about open-source software, I was reminded of one of my favorite video-games, The Battle for Wesnoth.
Basically, it is a combination Strategy/RPG where you lead an army against your enemies. Not very original, neh? What I believe makes this game quite unique is the fact that- aside from the fact that it is free to download and play!- the source-code is not protected. Basically, people who play the game are free to edit it and to add to it as they please. The programming language used for the editor is not simple, but it is also not impossible to learn (actually, a little experience with Deductive Logic may go a bit farther than computer programming language here). The only expectation of the players is that if they make some change to the maps/scenarios/sprites/etc, they should share it. That is it.
It's encouraging that there are communities like this on the intra-web. My only real wish is that someone would make the Reseau-Lu software open-source...and free!
P.S.: I do not accept any liability for time lost becuase you get addicted to the game.