If you use the Opera [operaubuntufonts, opera, opera9, operastaticbin, opera-idstring, operamini41, linkstashbuttonsforoperawin764bit, badoperasites, operaminiusage, operamini4] web browser (er, you are using Opera, right?), check out this integrated spell checker script called OSpell. It uses Opera's integrated JavaScript to enable in-place spell checking in web text boxes. Very nice!
But alas, like the official Opera spell checker, it does not have an "Ignore All" feature, at least so far as I can tell.
