What free games similar to minecraft are there?

Terraria? 2d mine craft.

1) Synthetic World

The open world feel to Minecraft is part of what makes it so much fun to play. Knowing that you could wander for days and create an entire world if you had the time is what keeps skilled creators playing day after day. Voxel games like Synthetic World by StaudSoft, which add an whole new layer of realism to this style of game was bound to happen eventually.

2) Cubelands

Cubelands may be newer, but it has a lot of polish. The game is online, supports multiplayer, and focuses on building a world with your friends using the objects and resources you find. It's available for Mac and PC, it's entirely free, and has a large community of registered players spread across a bunch of servers

3) Terraria

Terraria is what Minecraft would have been if it were a side-scrolling adventure game. In exchange for a massive, 3D open world, you get a massive 2D one, though you're more likely to reach the horizontal or vertical limits in Terraria than you are in Minecraft. Rather than crafting and building structures, Terraria is more focused on fighting and optimizing gear. Both games stress exploration and resource gathering equally.

4) Blockland

Blockland looks a bit like what would happen if Lego decided to make a Minecraft game. The characters are blocky and the world looks like it's been assembled with toy pieces. The game's developers actually make that comparison: they say it's "like playing with Legos on the internet.".