So now that all the Minecraft frenzy has died down, or at least leveled out. It's seems safe to talk about a new game called Minetest. Why? Well as you can see from the name. It is most definitely a Minecraft clone and a pretty decent one at that.
Why in the world would I be interested in a game like this? Well maybe you yourself haven't' gotten around to playing the famous Minecraft and don't feel like shelling out dough to try it out. Or perhaps you want to play Minecraft with all your "real" friends who don't have Minecraft and don't plan to buy it. Or perhaps you're just an open source fanboy who love C programming.
Whatever the reason, I would highly recommend trying it out as it's lighter on resources than the java based alternative and though not as polished, you can still build block related structures. Minetest also scales up really well (I've installed it on a netbook as a server) and has been improved over the years. There used to be no sound, bugs when random blocks would disappear, pirate looking player models and no moving water. but now we've got a decent clone. Playing on your own is definitely not as fun as enjoying it with your friends so setup a LAN party, blast some C418 soundtracks and enjoy!