(original link, no longer active – http://www.billmonk.com | Bill Monk) is a website that helps you to keep track of who owes what between friends, but without the social tension. It looks pretty fun.
2022-03-15 Update:
Alas, Bill Monk is no longer. May he rest in peace. You’ll have to do your own financial friend math.
Alas, Bill Monk is no longer. May he rest in peace. You’ll have to do your own financial friend math.