ADISC now has an official Minecraft server.
Minecraft is a survival/building game that is quite popular (millions of copies sold), and allows you great flexibility.
You can hunt monsters, build everything from factories to fortresses, explore the depths of the earth, etc, all by yourself or co-operatively with friends.
The world you play in is shared between all players, so you can also explore other peoples' creations.
For information about playing, click the "Minecraft" link in the nav bar at the top left of the page. Note that this link will only appear for Established Contributors and higher. Also note that the official minecraft server is an experiment (ADISC's first official games server) and subject to change over time.