http://minetest.net/ is a game that is heavily influenced by Minecraft's success, but has decided to take a different approach to gameplay and the modding capability of the game itself. I think the biggest difference, and probably the best reason to play MT, is that the base game itself is actually a mod. The engine lets you load 'game modules' to play. Third parties can easily create their own modules with almost any functionality and resources they want to add. There is even a module designed to specifically recreate some of Minecraft's functions. http://minetest.net/screenshots It takes some getting used to, and it is by no means a Minecraft replacement, but it does have the added bonus of Minecraft-like multiplayer for free.