I highly recommend playing this.
Free, but of course you can get special privileges if you donate.
basically, cube based building...
with 32 player mp
it's pretty crazy seeing what other people have built, personally i've spent over six hours building a gigantic golden tower with a roof garden, etc..
I suggest the gigantic map server. It has a rainbow road. Also, dont go randomly deleting blocks, you will get kicked (ground blocks are ok, but otherwise, leave it be.)