Astraware Sudoku - It's a different kind of Zen

Sudoku Links

Here are some useful Sudoku links:

Astraware Sudoku - official page for Astraware Sudoku software for iPhone, iPad, TouchPad, Nook, and more!
Simple Sudoku - another great PC based maker and solver.
Sudoku Wikipedia Entry - some good background info
The Sudoku Programmer's Forum - a bit extreme but really in-depth discussion on techniques.