Here is one software - *mos-page.ch.vu/ but it doesnt appear to be english...
Also, check out a software called Konfabulator... It is a software for which you can develop addons that do cool stuff - there was a sudoku generator available with it... it was good... also had a sudoku solver... The software has been acquired by yahoo and is available at *widgets.yahoo.com/ as Yahoo Widgets
Arun