Spring Grove Cemetery in Cincinnati. Lots of interesting and mature trees and numerous Champion trees. Get their address off the website and use Bing Maps to find it. I-75 exit 6 gets you in the ballpark. Cave Hill Cemetery in Louisville is reportedly very good as well, but I've never been there so can't say for sure.
Marshall

Here is a link that might be useful: The Arboretum at Spring Grove Cemetery

I would suggest a trip to Hidden Hill Nursery in S IN, about 8 lorth of Louisville. Though I have not made it there yet myself, I do plan a day trip sometime soon. I have heard he has a lot of things that are not what you would normally find at a nursery.

Wonderful tour on You Tube!

Here is a link that might be useful: Hidden Hill

Thanks very much for the recommendations! I'll check both locations out.

Any other ideas, especially around Louisville?