- Killer Samurai Sudoku - Offers printable samurai sudoku puzzles for download. Also provides rules and solution strategies.
- Math Games: Sudoku Variations - Offers detailed descriptions and illustrations of Sudoku variations, including Diagonal, Cubical, Even-Odd, and hybrids. Also includes a short history.
- Mathematical Recreations - Custom Word Doku puzzles devised by Steve Schaefer. Features an entire sentence embedded into the puzzle.
- Sudoku Samurai - Offers printable sudoku samurai puzzles for download.
- Sudokuto - Two-player variant. Offers several board sizes to play against the computer. [English/Norsk]