Minetest is a free, open source building game inspired by Minecraft.

Gnomescroll is an open source multiplayer voxel game.

Voxelands is a free voxel world game.

Dwarf Fortress (Slaves to Armok: God of Blood Chapter II: Dwarf Fortress) is a part construction and management simulation, part roguelike, indie video game.

Junk Jack is an action-adventure sandbox video game.