» Eijidoku    Word based version of the game.    http://www.eijidoku.com/

» Killer Samurai Sudoku    Offers printable samurai sudoku puzzles for download. Also provides rules and solution strategies.    http://www.killer-samurai.com/

» Math Games: Sudoku Variations    Offers detailed descriptions and illustrations of Sudoku variations, including Diagonal, Cubical, Even-Odd, and hybrids. Also includes a short history.    http://www.maa.org/editorial/mathgames/mathgames_09_05_05.html

» Mathematical Recreations    Custom Word Doku puzzles devised by Steve Schaefer. Features an entire sentence embedded into the puzzle.    http://www.mathrec.org/sudoku/

» Sudoku Samurai    Offers printable sudoku samurai puzzles for download.    http://www.binaryworlds.com/sudoku/

» Sudoku-Ball    A three dimensional version of the puzzle. Includes game rules, online version and news.    http://www.sudoku-ball.com/

» Sudokuto    Two-player variant. Offers several board sizes to play against the computer. [English/Norsk]    http://www.menneske.no/sudokuto/eng/