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!

EssentialPIM - EssentialPIM is a free Personal Information Manager that keeps up with the times and lets you manage appointments, tasks, notes, contacts, password entries and email messages across multiple devices and cloud applications.

/Tab - The simple way to split a bill among friends.

Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.

Dinngo - Splitting payments the fun and easy way

Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.