HoDoKu

How about a bit of puzzle this sunday afternoon? HoDoKu will have you covered. It's a Sudoku generator/solver/trainer/analyzer, so it can both generate puzzles for you, let you solve them, give hints, solve them for you and let you highlight various solving techniques so you can learn from them. It has loads of functions and the various analyzation tools, like the ability to see how far a certain "move" takes you toward the solution, sounds really cool. I had no idea a Sudoku game could be so complex, so this was a cool find.

HoDoKu in the middle of a game, complete with hints and a solution summary.