Splitwise - Splitwise is a free tool for friends and roommates to track bills and other shared expenses, so that everyone gets paid back. On the web, iPhone, and Android!
Halfdollar - Free and elaborate spreadsheet budgeting.
Tricount - Manage and share expenses with friends
BeeWise - Automagically track your daily expenses. No manual entry.
Splittable - Shared living made simple
Verse Groups - Group expenses and payments, simplified.