ComputerCraft

ComputerCraft is a mod (with full SMP support) which adds in-game computers. Each computer comes with its own Operating System featuring a host of built-in programs, and can be programmed to do anything you want with the easy-to-learn Lua programming language. Each computer has its own isolated file system and OS, a DOS-like screen interface, a comprehensive help system, two awesome games (including a text adventure based on Minecraft, and a fast paced ams like playing star wars or playing "Worm", an ASCII version of snake. ComputerCraft utilisesLua , an easy-to-learn programming language! 

Components include:

• Console
• Disk Drive
• Floppy Disk
• Modem
• Turtle
• Mining Turtle
• Wireless Turtle
• Wireless Mining Turtle
• Monitor

Bundled APIs

• Bit API
• Colors API
• ComputerCraft API
• Coroutine API
• Disk API
• Fs API
• Gps API
• Help API
• HTTP API
• IO API (from lua) - note that a number of functions don't exist or have bugs: http://www.computercraft.info/wiki/IO_(API)
• Keymapper API
• Math API (from lua)
• OS API
• Parallel API
• Peripheral API
• Rednet API
• Redstone API [abbr.: Rs]
• Shell API
• String API (from lua) - note that string.gmatch, .sub, .find have bugs: [1]
• Table API (from lua) - tutorial
• Term API - also see monitor.setTextScale
• Textutils API
• Turtle API
• Vector API