Dan Tull has created a wonderful Sudoku tool that makes Hard Sudoku puzzles less tedious, and Tough Sudoku puzzles possible!

You need to provide your own puzzle values, which is just takes a few double clicks and then you are off.  It basically does the grunt work of eliminating the obvious impossible values for you.

It could take hours of tedious re-evaluation to solve a tough puzzle manually and tough puzzles seem to require some guess and check as well.  With the tool, the re-evaluation is mostly free and guess is check is made much easier with the "Copy Puzzle" feature.

The tool is a Javascript application supported on IE, Firefox, and Safari.  The Copy Puzzle feature doesn't currently work in IE however.

Excellent work all around Dan, Thanks!  I'm still addicted, but at least I waste less time per day doing the harder puzzles.  :)