Today a free game was launched on Steam. Anyone that has steam is free to grab it and shoot it up. It's a 4 player coop, that pits the four humans against a crap ton of aliens in a top down 3d shoot-em-up.
The game ships with advanced modding tools and is highly customizable. I've played the single player training map once so far and it has some very addictive qualities.
It's limited to 4 players, we've got 6 guys from the Ioncross crew that have jumped in. Two of which seem to be on-board to modding the thing. So with some 5th interest we could get some real insanity going with both groups I think.