Rising from the Ranks: Rating for Multiplayer Games is an article on Gamasutra by old-school Quaker (and Loki Entertainment developer) Bernd Kreimeier, examining scoring and ranking systems such as those employed in ngWorldStats, which currently ranks multiplayer Quake II and Unreal Tournament games. The article makes a comparison to the ELO ratings of the chess-playing world, and while it is heavy on statistics and mathematics, it makes an interesting read if you're into this sort of thing.