Useful sites

Sudoku Games
A collection of various Sudoku games divided by difficulty, puzzle type, and type of grid.

Livewire Puzzles
Puzzle producer from Edmonton, Canada that makes hand made puzzles. These types of puzzles can be frustrating since once you figure out the solution they becomes really easy, and you might wonder how it took you so long to solve it. The site also got a fun section with sudoku and other puzzles.