OpenSky Sudoku Generator

I like it: OpenSky Sudoku Generator

The service lets you generate printable sudoku puzzles which you can download (as Acrobat PDF files), print, and then work out with pencil and paper.
The generator produces classic symmetrical puzzles of varying difficulty levels. The difficulty level ("Easy", "Medium", "Hard", "Very hard") appears on the printed page along with a difficulty factor ranging between 0.01 and 1.00 (the higher the value, the more difficult the puzzle).
Author declared he had not written the generator himself; it is part of the gnome-sudoku software, written by Thomas Mills Hinkle. He has simply made it possible to generate PDFs from the puzzles, and has hooked it up to the web...