The Airstream park in Crossville, TN has several lots for sale. Check out the "Classified" section of their new website.....
http://www.airstreamtcpc.org/
Although it's technically open for members year round, the main season is late March to early November. Most of the full timers that live there in the summer spend their winters in warmer climates.
There are several visitor lots available at $10 per night for Airstreamers and they will always find room for more visitors, even if it means placing you on an empty member's lot, so feel free to stop in and check them out.