Okay, so a while back I asked the question, "Do you Sudoku?" Well, our good friend, Tim Stall, has answered with a resounding yes.
Tim has designed a very impressive "Sudoku Toolbox." I played around with it today and really liked it. One of the things that separates this Sudoku site from others is that it explains why a move is or isn't allowed (if you ask for it).
Whether you're a seasoned Sudoku grandmaster or someone just interested in learning about the game, I'd encourage you to have a look; and if you agree that it's a fun and helpful site, I'd suggest you vote for it. "Sudoku Toolbox" is currently ranked #20 on Top 50 Sudoku Sites!