Asp.net 3.5 mvc 1.0 spell checker

Have a look at jquery spellchecker, this will handle your client side UI

http://code.google.com/p/jquery-spellchecker/[^]

You could then plug this in to a Controller Action that accesses whatever resource will perform the spell checking and provide the spelling alternatives

That example uses the Google API, but you could access anything you want such as NHunSpell[^]