What are some alternatives?
When comparing BillMonk and Tabbt, you can also consider the following products
SplittyPie - Create event, add users and their expenses.
Kittysplit - The easiest way of sharing costs with a group of friends
TabSplit - TabSplit allows users to keep track of their "social debts".
WieBetaaltWat - With WieBetaaltWat you can manage a list with your shared expenses.
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