After quite a bit of time in development, the MMO mod for Starcraft II aka Starcraft Universe is finally available in beta! Made entirely by fans and funded via Kickstarter, this game looks pretty incredible...
What's better is that it's entirely free for you to try if you download the Starcraft II starter edition (available right here). So right now you're thinking "okay great an MMO for Starcraft II but what can I actually do?" As of right now, the beta only contains singleplayer tutorial and a basic raid for multiplayer. The game is expected to release in full come late August.