Since the AJAX => Perl => C gateway version was kinda crufty, I rewrote the Sudoku solver in pure JavaScript. It's not as fast as the other version, but it runs entirely in your browser and it's now animated! :)
Interested parties may find the JavaScript source available under the terms of the GPL.
Feb 2011 - Improvements in your browser's JavaScript engine over the past five years or so may result in the "pretty solve" button not actually updating the visual display until the script is done. Sorry. On the balance, this is probably a good thing, though.
8 - values you provided
8 - values we calculated
8 - impossible value you entered
fast solve - solves the puzzle
pretty solve - solves the puzzle, with animation
reset - clears the solution squares
clear - clears everything