Splitwise is the best way to share bills and IOUs and make sure that everyone gets paid back.
Use Splitwise to split household bills with roommates, to figure out costs for a group vacation, or just to remember when a friend spots you for lunch. On the iPhone, Android or the web (http://splitwise.com), you can view your balances, track spending trends, set up email reminders for bills, and much much more!
"I only wish such a tool had been available when I was a new college graduate..." – Ann Carrns, NYTimes Bucks blog "Whoa, @split_wise is what we always wanted livewith.us to be. Totally going to use this in my new apt instead of my own software." – @aroldan