The Xbox.com website has been updated ahead of the new dashboard launch (which just went out to preview members). With the update comes a new host of social features, designed to help Xbox gamers find other players looking to play the same games you are. Need a co-op partner for Modern Warfare 3? No problem.
Your home page on Xbox now lists your friend's recent activity by game. So that means if you've had 30 some friends play Gears of War 3 recently, that would show up. You could then see just what friends had played it making it easier to message a few to get a game of Horde together. But that's only one way.
The other major addition is something called Beacons and this is tied directly into the new dashboard. Basically the way it works is you go in and say - tonight I'd like to play Game X. That's your beacon. Now go about your business and play whatever, but everyone on your friends list can see that you are looking to play Game X. These beacons also extend to the website so friends can check who is online and looking to play what with relative ease.
All of this sounds very promising for co-op gamers looking to find partners. The Xbox Dashboard update should be available soon to everyone.