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!
ELFSH - ELFSH alows coordinating eating together
LetsPayTheBill.com - Free online tool to calculate the distribution of expenses during a group activity.
Kittysplit - The easiest way of sharing costs with a group of friends
SplittyPie - Create event, add users and their expenses.
Tricount - Manage and share expenses with friends