Minetest

Minetest is designed to be simple, stable and portable. It is light enough to work even on relatively old hardware. It currently runs on a laptop with Intel 945GM graphics. Although DualCore is recommended.

Features:

• Walking around and digging, building in an endless voxel world along with crafts and resource items to help you along the way
• Simplifying Modding API that supports many kinds of additions and modifications to the game
• Multiplayer for dozens of players, via servers hosted by users
• Voxel based lighting with in-game consequences (light caves and buildings with torches)
• Nearly infinite world and beautiful map generator
• Runs natively on Windows, Linux, OS X and FreeBSD.
• Supports multiple languages that have been translated by the community