Sudoku Forum - A forum for fans as well as people wanting to learn more about Sudoku. - http://forum.ringsworld.com/sudoku.html
Sudoku Programmers Forum - Discussion forum for developers of programs such as creators, helpers, and solvers. Discussions include solving techniques, creating puzzles, mathematics, and variants. - http://www.setbb.com/phpbb/?mforum=sudoku
Sudoku Players - The sudoku.com forums. Includes discussion on solving techniques, solver programs, downloadable puzzles, sudoku for juniors and the puzzles printed in different newspapers from around the world. - http://www.sudoku.com/forums/