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!
Halfdollar - Free and elaborate spreadsheet budgeting.
Splittable - Shared living made simple
Budgy 2 - Your best free budget assistant on the go
EquiTable - Split the bill fairly
Budgt - Track your ramen spending (iOS)