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!
ihatemoney - Manage your shared expenses, easily
Spliit - Free and Open Source Alternative to Splitwise. Share expenses with your friends and family.
Tricount - Manage and share expenses with friends
MoneyBuster - Multi-project shared budget manager able to sync with self hosted FOSS services
SplittyPie - Create event, add users and their expenses.