Christiaan Olie - Personal page describing Sudoku, rules, strategies, and offering puzzles to print. [Dutch/English]
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.
Dan Rice's Sudoku Blog - Weblog discussing techniques for creating and solving puzzles, including hard puzzles. Also offers a daily puzzle.
Flying Frog Consultancy - This web page describes a 19-line (769-byte) OCaml program that solves Sudoku puzzles.
Gaby Vanhegan - Daily and random puzzles at six difficulty levels, Flash and JavaScript solvers, solving techniques and glossary of terms.
Grant Gibson - Offers syndicated puzzles for websites as well as print publications.
The Heebie Su Doku Site - Offers a glossary of terms, links to puzzles and variants, and tips for solving.
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.
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.
Play Sudoku - Flash version of the Sudoku game. Also offers solution.
Prize Sudoku - Offers competitions for prizes. Traditional Sudoku, Godoku (letters) and Super Sudoku (16x16).
Puzzle Bus - Offers a daily puzzle, books, software, and related merchandise. Also offers puzzles for syndication.
Scanraid LTD Search Technologies - Sudoku Solver by Andrew Stuart. Shows the logic behind solving sample games square by square.
Sudoku Place - Offers daily puzzle in PDF format. Includes archive, FAQ, and a "dozen" variant.
Sudoku Puzzles - Free daily puzzles with five difficulty levels with their solutions. Also offers guide to solve Sudoku puzzles.
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]
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.
SuDoKu-Cracker - 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.
SuDokuMate - SuDokuMate is a SuDoku Helper (not a Solver) that replaces pencil and paper to aid solving.
Sudoku-san - Free daily puzzles with four difficulty levels. Also offers a solving assistant and downloadable e-book collections for purchase.
SudokusWeb.com - Free daily printable Sudokus. Also offers history, rules, and solving techniques. [English/Spanish/French/Catalan/German/Portuguese]
Sudoweb - Free daily puzzles with five difficulty levels. Also offers printable e-book.
The Times Sudoku - Daily sudoku and killer sudoku puzzles from The Times newspaper, London.
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 variants of Sudoku. Notes that these are a type of "latin square" which have been analyzed since ancient times.
World Sudoku Championship - Information on the 2006 World Sudoku Championship held in Italy. Includes background information, events, results and FAQ. [English, Italian]