http://www.xboxlink.co.uk/
You can download the beta from here to test it out, and go to #xbox-link on efnet to organise matches, meet other gamers, ask questions etc. It has 2 modes of play, a messenger mode where you can add peoples tags and line up games with people you play regularly by pm, and worldwide gaming mode (WGN) which acts as one big LAN with everybody in the world who is using WGN available to play against.
Social Networking Bookmarks