Good Old Tetris - Play Tetris Online. The game that will never get old.
OpenBlok - A customizable, cross platform, open-source falling block game, packed with a bunch of features.
Blockinger - An open source Tetris clone for Android.
Puyo Puyo Champions - Fun, fast-paced, competitive puzzle action!
NullpoMino - NullpoMino is an open-source action puzzle game that works on the Java platform.
Hextris - An addictive puzzle game inspired by Tetris.