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!
Tricount - Manage and share expenses with friends
Splittable - Shared living made simple
EquiTable - Split the bill fairly
Kittysplit - The easiest way of sharing costs with a group of friends
Dinngo - Splitting payments the fun and easy way