Daily SuDoku
- http://www.dailysudoku.co.uk/
- Offers daily printable puzzles of varying difficulties, including Sudoku for Kids. Also offers archive of past puzzles, tool for rendering custom puzzles, FAQ, and books for purchase.
Gaby Vanhegan
- http://vanhegan.net/sudoku/
- Daily and random puzzles at six difficulty levels, Flash and JavaScript solvers, solving techniques and glossary of terms.
SuDoKu-Cracker
- http://www.the24net.com/sudoku/
- Only creates puzzles with a "unique solution". The built-in generator has six different levels of difficulty and can generate many (millions) different puzzles. All puzzles can be printed, exported, saved and opened again.
Sudoku
- http://www.sudoku.li/english/
- History, instructions, variants and puzzles in four difficulty levels (PDF format). [German/French/English/Spanish/Italian]
Sudoku
- http://www.sudokutoday.com
- Provides sudoku puzzles in easy, medium and hard levels with their solutions. Also provides facility for daily email sudoku newsletter.
Sudoku Puzzles
- http://www.sudokupuzz.com
- Free daily puzzles with five difficulty levels with their solutions. Also offers guide to solve Sudoku puzzles.
Sudoku Puzzles
- http://www.sudoku-puzzles.net/
- Offers four difficulty levels. The puzzles can be solved online or downloaded as a PDF file. [English/German/French/Spanish/Dutch/Portuguese/Italian]
Sudoku-san
- http://www.sudokusan.com/
- Free daily puzzles with four difficulty levels. Also offers a solving assistant and downloadable e-book collections for purchase.
Sudoku.com
- http://www.sudoku.com/
- Includes an overview of how Sudoku is solved, a monthly contest and a downloadable Sudoku game. Also includes a kids section and discussion forums.
SudokusWeb.com
- http://www.sudokusweb.com/
- Free daily printable Sudokus. Also offers history, rules, and solving techniques. [English/Spanish/French/Catalan/German/Portuguese]
Wikipedia: Sudoku
- http://en.wikipedia.org/wiki/Sudoku
- An encyclopedia entry describing the rules, history, strategies and variants of Sudoku. Notes that these are a type of "latin square" which have been analyzed since ancient times.
World Sudoku Championship
- http://www.wsc2006.com/
- Information on the 2006 World Sudoku Championship held in Italy. Includes background information, events, results and FAQ. [English, Italian]