Manic Digger is probably the most popular and functional Minecraft clone currently available. I downloaded it and play tested it to see if it was even remotely close to providing the same sort of experience that Minecraft does. (Spoiler: It’s not.)
At first, Manic Digger appears to be a very sold Minecraft clone. The block types are very similar to those in Minecraft and so is their appearance, but that unfortunately, is where similarities end fairly abruptly.