There is a modification now, for 6.x:
Spell Check It uses SpellCheck.net. Thanks to AllenAyres for it.
This one is English only. So I am guessing this request will still be up for some time till we get multiple language checking.
Done some searching:
There is a neat, and similar spellchecker.net, that is bilingual, Spanish and English. Id like this one.
Word Magic Then there is
SpellOnLine, with English, French, Italian, Portuguese and Spanish.
And anotherone, right now it is "being upgraded" so Im not sure if it has more languages other than English.
SpellCheck Free URL