KLOV: Tetris - http://www.klov.com/T/Tetris.html Information about the arcade versions of Tetris.
Tetris Lovers - http://members.tripod.com/~tetrislovers/ News, tips, screen shots, music, and information
Tetris Tips - http://angelfire.com/la2/tetris/tetris.html Provides hints for higher scores.
Wikipedia - http://en.wikipedia.org/wiki/Tetris Encyclopedia articles.
