Free sudoku puzzles

I have been tasked to find as many free and hard Sudoku puzzles on the net as possible to feed a recent addict.

Some sites offer "sample" puzzles while many others provide a few free puzzles a day. The Times is quite generous, since it archives around 2 weeks of Sudoku puzzles. But many of them are relatively easy and not what I am after.

I finally come up with 2 sites:

1. Free Sudokus by KrazyDad - free, 5 levels of difficulty, hundreds of Sudokus per difficulty level, in pdf files. Great for offline playing.

2. Web Sudoku - Millions of free Sudokus in 4 levels of difficulty. Choose a difficulty level and press for a randomly drawn puzzle for online playing. Time taken to solve the puzzle is recorded to compare yourself with the "norm". Even allow for "pencil marking" (i.e. entering multiple numbers in a single cell to aid thinking). Excellent for online playing.

These 2 sites should offer Sudoku addicts years of playing pleasure. Unless of course if they insist on playing hand-constructed Sudokus. Or unless if they, as I predicted, become fed up with this game soon.