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

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/

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

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

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

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