Yeah, there's always neat cars in the parking lot at most road courses.
As for other stuff....
If you're at Watkins Glen, you have to stop in at the Seneca Lodge and at least get a drink. The WG motorsports museum, the actual "glen" and the nearby aviation museum are all neat things too. And there are some good wine festivals in that area.
At New Jersey Motorsports Park, you are roughly mid-point between Atlantic City and Cape May........so you can choose your "poison" (I'd take Cape May).
If you go out to BeaveRun, I'd try to see the National Aviary in Pittsburgh and maybe "The Incline".
If you go to Summit Point, Mr. Scott has a darn nice collection of antique tractors (many of them Porsches!) on site.