Bukkit Plugins
I created and maintain a few plugins for the popular Minecraft server version/mod/whatever "Bukkit".
Most of these plugins are released on dev.bukkit.org, dev builds (bleeding-edge) are available on my Jenkins server and their source code is hosted on GitHub.
But I've also made a few non-public plugins. :P
TWLan
This is not "my project", but I'm part of it.
TWLan (short for "Tribal Wars LAN") is a remake of the popular browser game "Tribal Wars", aimed to be hosted and played in local networks with friends.
You have a whole game world for you and your friends, you can game games speeds way above the ones on the official servers and there are a lot of modifications available.