9x9, 6x6 and Samurai Sudoku - Offers classic Sudoku and variants, as well as an online solver.
Meta Description: [ Sudoku - The Latest Puzzling Craze. Complete Puzzles - 6x6 or 9x9 and use the Puzzle Solver. Find out about the History and Origins of Sudoku ]

BBC News: The puzzling popularity of Su Doku - Article by Paula Dear. Covers history in Japan and the UK and compares to the Rubik's cube craze of the 80s.
Meta Description: [ Su Doku, a crossword-style brainteaser which uses numbers instead of letters, has become the focus of a national newspaper circulation war. Its success is, frankly, puzzling. ]

Christiaan Olie - Personal page describing Sudoku, rules, strategies, and offering puzzles to print. [Dutch/English]
Meta Description: [ Sudoku,Online Suduku, Sudoku, Sudokupuzzle, sudokupuzzles, sudoku's, sudoko, suduku, sodoko, suduko, sudoku, soduko, soduku, sodoku, soduku ]

Daily SuDoku - 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.

Daily Sudoku - Offers a different printable puzzle each day. Also includes solutions and FAQ.
Meta Description: [ Sudoku and Sudoku puzzle is a fun puzzle is to enter a number from 1 through 9 in each cell of a Sudoku grid, most frequently a 9×9 grid made up of 3×3 subgrids (called 'regions'), starting with various numbers given in some cells (the 'givens') ]

Dan Rice's Sudoku Blog - Blog discussing techniques for creating and solving puzzles, including hard puzzles. Also offers a daily puzzle.
Meta Description: [ Tips on solving and generating Sudoku number puzzles ]

Flying Frog Consultancy - This web page describes a 19-line (769-byte) OCaml program that solves Sudoku puzzles.
Meta Description: [ A program to solve Sudoku puzzles, written in OCaml ]

500 Fundoku - Randomly generated puzzles at three difficulty levels.
Meta Description: [ Fundoku offers free beginner and expert sudoku puzzles for you to print, plus Sudoku history and tips! ]

Gaby Vanhegan - Daily and random puzzles at six difficulty levels, Flash and JavaScript solvers, solving techniques and glossary of terms.
Meta Description: [ More than a million free Sudoku puzzles, useful solving tools, basic and advanced solving techniques, dictionary of terms, and sudoku merchandise. Play, print, download them as a PDF, email to a friend, save your progress, or download a free PDF book of puzzles. Built-in Syndication service, us... ]

Grant Gibson - Offers syndicated puzzles for websites as well as print publications.

404 Heebie.co.uk - News and puzzles.

Hirofumi Fujiwara's Sudoku - Offers a tutorial for creating puzzles, a Java-based solver, and links to other resources. [English/Japanese]

Information For Beginners - Collection of printable grids, ordered by difficulty level. Solutions provided. Includes rules and solving methods.
Meta Description: [ Sudoku Puzzles For Beginners contains a collection of sudokus, ordered by difficulty level. ]

404 Knight Features - Publishing syndicate in the UK and Ireland. Offers several variations, including classic, colour, kids, and Sudoku Word.

Maths Is Fun - Offers a number of applications and solvers for a variety of platforms. Also offers custom puzzles.

Minimum Sudoku - A project collecting Sudoku with the smallest number of givens that are still uniquely solvable. Offers the puzzle for download in text format.

My Days Are Numbered - An article by Seth Stevenson offering a brief overview of Sudoku.
Meta Description: [ When Slate asked me to write about "sudoku"—the number puzzle that's taken Britain by storm (and seems poised to conquer the United States, too)—I thought it might be a pleasant little assignment. After all, I like puzzles. I'm always up for trying a new o ]

404 Nikoli - From the company that introduced the game to Japan in 1984. Description, history, tutorial, and instructions on constructing custom puzzles.

Prize Sudoku - Offers competitions for prizes. Traditional Sudoku, Godoku (letters) and Super Sudoku (16x16).
Meta Description: [ Win prizes with our Super Sudoku competition. Sudoku solvers and generators for 9x9 Sudoku, 16x16 Super Sudoku, 5-grid Samurai Sudoku and Godoku puzzles ]

Puzzle Bus - Offers a daily puzzle, books, software, and related merchandise. Also offers puzzles for syndication.
Meta Description: [ Great games and free stuff for the sudoku player. Daily Su doku puzzles and grids. Software, Books and gifts. Professional service for publications. Website Goodies. ]

404 Puzzle Japan - Offers tutorial, downloadable puzzles (PDF format), and a Java applet.
Meta Description: [ This site releases at least three new puzzles every day. There are seven different puzzle types. Membership costs just $3.99 per month. There are free sample problems. ]

Simple Sudoku Solver - JavaScript brute force solver.
Meta Description: [ Simple Sudoku Solver, written in JavaScript ]

Sky One - Information on UK-based cellular provider's world-record largest Sudoku puzzle and accompanying contest.
Meta Description: [ Sky One is the UK's most popular non-terrestrial entertainment TV channel and the UK home of high-quality programming. Key shows on the channel include; The Simpsons, 24, Dream Team, Enterprise, Malcolm in the Middle, Nip Tuck, Brainiac, Deadwood, Hex, The 4400, Long Way Round, Battlestar Galacti... ]

SolveMySudoku.com - Browser-based puzzle solver.
Meta Description: [ A free online sudoku puzzle solver ]

Solving Sudoku - Step by step guide to solving sudoku puzzles. Goes from basic to advanced techniques.
Meta Description: [ Rules and hints for solving Sudoku puzzles. ]

Sudoku - Free daily puzzle with solution. Includes archive of past puzzles.
Meta Description: [ Free Sudokus! Every day, a new sudoku with the solution. ]

Sudoku - Provides sudoku puzzles in easy, medium and hard levels with their solutions. Also provides facility for daily email sudoku newsletter.
Meta Description: [ Sudoku today provides a lot of sudoku puzzles in easy, medium and hard levels. ]

Sudoku Addict - Offers printable grids and solution walkthroughs.
Meta Description: [ Sudoku is the new number puzzle driving people around the country crazy. Also known as Number Place in the US it is deceptively simple, you can start a puzzle and find yourself still racking your brain a few hours later. ]

Sudoku enumeration - Several programs in different languages for analyzing possible Sudoku combinations.

Sudoku Fun Puzzles - A website representation of Sudoku, the broad sheet newspaper puzzle imported from Japan. Leaderboard lets players compare completion times.

Sudoku Helper - Free online helper application. Shows options for each square, and allows backtrack, restart, or save.
Meta Description: [ Throw away your pencil and eraser, forget struggling with Excel. This program presents the Playing area on screen showing both known numbers and the options for unfilled cells. ]

Sudoku Madness - Seven days of daily puzzles.

500 Sudoku Master - Free daily grids that can be printed. Also offers solution and archive.
Meta Description: [ Free daily sudoku puzzle ]

Sudoku Online - Includes Sudoku tips and strategies as well as a downloadable game and a 3D Sudoku puzzle.
Meta Description: [ Sudoku tips, strategies, information and help from Michael Mepham for London Daily Telegraph and Los Angeles Times solvers. ]

Sudoku Online Solver from friko.net - Free online generator, solver, and helper. [English/French/Spanish/Polish]
Meta Description: [ SUDOKU ONLINE SOLVER allows to generate random, to solve given or generated SUDOKU puzzles, as well as to support solution and print ]

Sudoku Place - Offers daily puzzle in PDF format. Includes archive, FAQ, and a dozen variant.
Meta Description: [ Free daily printable sudoku puzzles - plus an archive, jigsaw sudoku and the Sunday Su Dozen ]

Sudoku Puzzles - Offers four difficulty levels. The puzzles can be solved online or downloaded as a PDF file. [English/German/French/Spanish/Dutch/Portuguese/Italian]
Meta Description: [ Here you find lots of free Sudoku puzzles. The puzzles can be played online, printed out and even exported as PDF-File. ]

Sudoku-san - Free daily puzzles with four difficulty levels. Also offers a solving assistant and downloadable e-book collections for purchase.
Meta Description: [ Sudoku-san, your Sudoku Assistant - Daily puzzles, tools to help you, and suggestions to improve your play ]

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.
Meta Description: [ Sudoku, Powered by RealArcade - the Home for Sudoku, Free Sudoku Games, Pappocom Sudoku Puzzle Solutions and Sudoku Players’ Forums. ]

Sudoku.li - History, instructions, variants and puzzles in four difficulty levels (PDF format). [German/French/English/Spanish/Italian]

SuDokuMate - SuDokuMate is a SuDoku Helper (not a Solver) that replaces pencil and paper to aid solving.
Meta Description: [ Stop having to rub it all out and start again! ]

SudokusWeb.com - Free daily printable Sudokus. Also offers history, rules, and solving techniques. [English/Spanish/French/Catalan/German/Portuguese]

The Daily Sudoku - Today's daily Sudoku puzzle from www.dailysudoku.co.uk.

The Economist: Do you sudoku? - Article on the puzzle's popularity in the United Kingdom and elsewhere.

The Guardian: So you thought Sudoku came from the Land of the Rising Sun... - Article by David Smith covering the puzzle's origins as Number Place by Dell Puzzle Magazine in New York in the 1970s.

The Guardian: Sudoku fever grips UK newspaper readers - By Stephen Brook. Article covers how the UK craze got started.
Meta Description: [ 5.45pm: The Sudoku entered the mainstream today when the Sun published its version of the addictive Japanese puzzle. By Stephen Brook. ]

The Heebie Su Doku Site - Offers a glossary of terms, links to puzzles and variants, and tips for solving.
Meta Description: [ Everything there is to know about Sudoku, Downloads, fun links, terminology index, kakuro, variations (16x16, killer, samurai etc) and tactics - all in nine different languages! ]

The Sudoku Grandmaster - Self-styled Grandmaster offers tips on life as Sudoku, humorous claims of achievement, and a daily puzzle.
Meta Description: [ The Official homepage of the World's only Sudoku Grandmaster. ]

The Times - Articles and puzzles from The Times (London).
Meta Description: [ Play daily Sudoku and Killer Sudoku puzzles from the newspaper that introduced Sudoku to the UK ]

Universal Press Syndicate - Offers monochrome and color grids and variations for online and print syndication. Information on syndication as well as an interview with creator David Bodycombe.

Vegard Hanssen's page - Offers a database of crafted puzzles, organized by difficulty. Also offers FAQ and forum. [Norwegian/English]

Wikipedia: Sudoku - An encyclopedia entry describing the rules, history, strategies and varients of Sudoku.

Yosmany.net - Offers HTML to add a JavaScript-based puzzle to any site. [English/Spanish]