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!
Kittysplit - The easiest way of sharing costs with a group of friends
SplittyPie - Create event, add users and their expenses.
WieBetaaltWat - With WieBetaaltWat you can manage a list with your shared expenses.
ihatemoney - Manage your shared expenses, easily
Tricount - Manage and share expenses with friends