On sale on the steam store at the moment is Starforge
"StarForge is a game about gathering resources, building bases, crafting anything you want, and surviving on an alien planet. Earth's star is dying and humanity transferred as much technology and resources as possible and left on a one way mission to populate another planet.
StarForge was inspired by Halo, Warcraft 3, Borderlands, Terraria, and Minecraft. It borrows elements from the RTS, FPS, RPG, Voxel Builder, Tower Defense, and Physics Sandbox genres. We are building a dark and serious universe and want the player to live out their own unique story on the procedural planet."
its still in alpha, but here is a video
http://www.youtube.com/watch?v=YxBSYit49c8
and its on sale now and its mutiplayer