The Hocking Hills area of Ohio is just gorgeous if you can make the stop (near Logan, OH Southeast of Columbus):
Hocking Hills Ohio | Official Visitors Website - hockinghills.com
(A good place to camp there is the
Hocking Hills KOA be warned, though, the entrance drive is quite steep.)
Otherwise, if you stay on I-80/90 to/from Cleveland to get to I-77 you can stop at the Rock and Roll hall of fame right in downtown Cleveland (and the NFL hall of fame near Akron) depending on your interests.
If you are inclined to amusement parks, Cedar Point boasts the most roller coasters of any park (also along 80/90 near Sandusky, OH:
Cedar Point).
Note that the RV areas in the service plaza's on 80/90 in Ohio are some of the best of any turnpike around (at least the ones we've been to).