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/
