Asymmetrical Sudoku: Includes a generator and solver.
Bob Hanson's Sudoku Assistant: JavaScript-based gameboard and solver. Can use cross-hatch scanning and subset elimination.
BrainBashers: Offers daily puzzle in one of three difficulty levels. Archive of daily puzzles and an assistant.
Braingle Sudoku: Interactive sudoku game with high score tracking. Includes solution strategies.
Count to Nine: Offers five difficulty levels, timer, solution, and printable view.
Daily Sudoku Puzzle: Offers daily timed puzzle and four difficulty levels. [English/Portuguese/Spanish/German/French/Italian]
Fiendish Sudoku: Free daily sudoku puzzles at five difficulty levels. Online solving grid with hints and step-by-step solutions.
Free Sudokus: Offers hints, solution checking and grids in sizes other than 3x3.
Goobix.com: Offers up to four difficulty levels.
Jaap Scherphuis' Generator: Java-based generator offers four levels of difficulty. Includes view of solution.
Number Logic: Offers a new timed game daily, with a validator and four difficulty levels.
Paul's Pages: Offers random, crafted, and non-standard puzzles. Includes hints and import/export tool.
Play Sudoku: JavaScript-based Sudoku, available for syndication on other sites.
Play Sudoku: Registered users can save unsolved puzzles and high scores are kept at three difficulty levels. Also offers rules and tips for solving. [English/Russian/German]
Puzzles4Free.com: Free sudoku puzzles daily for you to solve. New puzzles every day.
Ridiculopathy - Sudoku Shuffle: Play with letters or numbers in the grid. Includes high scores, hints and move verification. [Requires Flash]
Seeing With C - Sudoku Solver: A solver program with an article explaining the algorithm used.
Su-Doku.net: Offers daily puzzle, downloadable games, and instructions.
Sudoku: Japanese puzzle game played by placing numbers in a grid so that each number only appears once in each row, column, and region. Offers three difficulty levels.
Sudoku by Froggy: Generates 2x2, 3x3, and 5x5 puzzles with adjustable level of difficulty.
Sudoku Central: Offers daily puzzle for printing. Also includes archive, online solver, and solving tips.
Sudoku Hints: Offers daily web-based puzzles with five difficulty levels. Includes solver, helper, and XML feed.
Sudoku League: League of online competitors. Scoreboard, rules, FAQ, hall of fame, and instructions. [English/Czech]
Sudoku Prime: Offers three difficulty levels and the ability to play against other players. [Requires Shockwave]
Sudoku Puzzles: Daily puzzles offered at four difficulty levels, available for play online or printed out. Includes rules and archives.
SudokuDave: Easy to very difficult puzzles that you can play online or print out.
Top Notch Su Doku: Offers several web-based alternatives, including Worduku, code-duku, and Samurai sudoku. Also offers a web-based solver.
Web Sudoku: Free puzzles with difficulty levels ranging from easy to evil. Provides print and online syndication.