OpenComputers is a Minecraft mod that adds programmable computers and robots to the game. The built-in computer implementation uses Lua 5.2 and is fully persistent. This means programs will continue running across reloads. For more information, please see the wiki. Feel invited to visit the community forums or drop by in the IRC channel #oc on esper.net.
A few useful links:
The OpenComputers documentation is available in a number of languages: