I downloaded HTMLPad 2002 Pro and it seemed quite fine to me . But I'm from Russia so I made russian dictionary for it. It have 89000 words. If you want to put it on your site write to warvik@mail.ru and I'll send it to you.
And I've got a small trouble... Two dictionaries (Russian+English) don't work together... So I have to put all words in one file... Maybe you can make option to use several dictionaries at once?