Blockland

[Wolvemarine]

Well it may seem a bit simple, but building blocks really hasn't ever been so fun.
And it being non-competitive adds to that.
Its freeware and already has quite a large cult gathering.
The controls can be a bit tricky at first but you can reconfigure them.
Its basically lego but its great fun when you get into it ^^.
http://www.blockland.us/blockland/index.asp?

I said it was freeware and it will be for a shortwhile longer, although the current versino is pretty much bug-free, there looks to be a retail only version coming out sometime in the distant future meaning no updates for free version im guessing.