From N.Central PA to Lima
I ran this route out and back to Maine last September and can give a few pointers. First, Rt. 6 (picked up south of Elmira, NY) is a great shot across PA. The Grand Canyon of PA is very scenic and worth the stop. I camped at the Colton Pt. St. Park (west side of Canyon) and found the views and camping more than adequate. Unfortunatly on my way back I got to enjoy Hurricane Ivan from the Adirondack's down (avoid storms with names :doh ).
Take Rt. 6 to the Allegheny National Forest and jump on Rt. 666 through the forest. It lives up to it's name, and just watch your speed.
From there pick up Rt. 62 through Oil City to Greenville and straight through to Rt. 88 in Ohio. Cross Mosquito Lake on Rt. 88 and follow all the way to Ravenna, OH (you'll pass the Krispy Creme Offices).
As a side note, there is no great way to avoid the Cleveland/Akron/Canton area (lots of congestion and traffic lights) and this is the best way I've found so far (other than interstate).
In Ravenna pick up Rt. 44 south all the way to Rt. 62 into Canton. You will go right by the Football Hall of Fame (if you're into it) and then take Rt. 30 all the way to Mansfield. There is construction off and on but Rt. 30 east of Mansfield is not too bad. This will put you close to the Mid-Ohio track (just sw of Mansfield in Lexington) for track day or on the return run for the Superbike races on Sunday. Route 30 and 309 split on the west side of Mansfield and I'd vote for 309 as well on into Lima. St. Rt. 314 S. from 309 is a clean shot down to Mid Ohio.
Enjoy the ride!