Where can one find good camping suggestions?

Can anyone suggest a book or website that lists great suggestions for camping by city, state, or part of the country?

I'm trying to find great state parks, national parks, corps of engineers parks, and other places in the midwest/southeast within a day's drive of Nashville. I know there have to be some hidden "gems" out there, but I can't seem to find a good source for suggestions.

Thanks!

- Mark