Schedule Share - Create and share read-only calendars
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!
Ddays - Plan events with friends without the back and forth messages
ihatemoney - Manage your shared expenses, easily
emble - Plan better events with your friends
Tricount - Manage and share expenses with friends