OpenBlok - A customizable, cross platform, open-source falling block game, packed with a bunch of features.
Good Old Tetris - Play Tetris Online. The game that will never get old.
Hextris - An addictive puzzle game inspired by Tetris.
Blockinger - An open source Tetris clone for Android.
Cuyo - An open source Tetris-style puzzle game for up to two players.
NullpoMino - NullpoMino is an open-source action puzzle game that works on the Java platform.