I use (and love) ieSpell - A Spell Checker for Internet Explorer but it seems I may have uncovered a bit of a bias on their part.
I was answering a post on the phpBB Support Forums today in which I made reference to both GoogleBot and MSNbot. These are automated systems that scan web sites and include them in the search engines.
When I spell checked my post before submitting, ieSpell caught both words and offered suggestions. Note that in some cases, ieSpell just tries to correct capitalization.
So tell us, ieSpell, what do you really think of MSNbot?