Cosmic Cow Games are running a free open beta of their new cute MMO - Cubic Castles. It's very much a 3D platformer with a Mario-esque flavour and a visual style like a polished minecraft for the terrain. In fact the visual cues will mean minecrafters will feel right at home, though the big block-ness is restricted to the terrain engine, with characters and other environment decorations like trees having more typical 3D representation. There is crafting and world building as you build your castle from surrounding materials, yet already this game is looking pretty polished for a beta release. But that's not surprising since some of the dev team have come from Pop Cap so they ought to know a thing or two about making polished games.
Download available from the Cubic Castles website