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.

NullpoMino - NullpoMino is an open-source action puzzle game that works on the Java platform.

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

Blockinger - An open source Tetris clone for Android.

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

Good Old Tetris - Play Tetris Online. The game that will never get old.