AI War on Co-Optimus.

From the post:

I checked out the demo last week and came away surprised just how deep this game is.  The game isn't for the faint of heart when it comes to strategy.  Thankfully there's a full tutorial available to walk you through the game.  The cooperative mode feels very robust, but you'll definitely want to use some sort of voice chat software because there's so much stuff to communicate.

Head over to Co-Optimus for the full post.