Mammoth Cave area is pretty cool. Probably good to research and book tours beforehand, especially going during peak tourism season.
I'd rate the Corvette Museum in Bowling Green an emphatic "OK". Not amazing, but I'm not real into Corvettes. As of a few weeks ago they had the mangled cars they pulled out of the sinkhole on display, so that was cool. There is a separate factory tour you can get on through GM that sounded interesting, but have to book at least a week in advance IIRC.
Louisville Slugger museum & factory in Louisville is worth spending an hour or two if you're in town. Not a real big place, but you see the process pretty close-up on the tour and they have a lot of significant memorabilia. There's a spot you can pose and take pictures with game-used bats from Mickey Mantle, Cal Ripken, etc and batting cages that you can take BP using exact model bats of several MLB stars past and present.