The best are Crosby Gardens Festival of the Arts (June), Ann Arbor Festival (July), Levis Commons Art Fair (August). Also good are Black Swamp (BG-August or Sept, I think), Old West End. You should apply to join the http://www.toledocraftsmansguild.org/
There are loads of smaller fairs also. Ann Arbor is really 4 festivals. Also most of the ones I mentioned are juried and that process is already over for this year.