Terraria - Dig, Fight, Build! The very world is at your fingertips as you fight for survival, fortune, and glory.
Minetest - Minetest is a near-infinite-world block sandbox game and a game engine, inspired by InfiniMiner...
The Blockheads - Night is falling and your blockhead is freezing.
Minecraft - A block-building game that allows you to create and explore entire worlds from scratch.
Terasology - Terasology (started under the name Blockmania) is an open source project started by Benjamin...
Blockland - Blockland is a non-competitive multiplayer sandbox-style construction game. It's kind of like playing with legos on the internet.