GamaSutra has a good article on rating systems at
http://www.gamasutra.com/features/20000 ... ier_01.htm
If it doesn't make it through the filter, try a google search for "Elo rating multiplayer, it's about the second or third result.
As far as the team scenario goes, what I suspect is that you'll find there's a fairly simple way to allow for that, some version of calculating the individual result against the average or a weighted average of the opposing team, or just compare a weighted average of the two teams (how to weight it would be the tough question).
--Dave
