Elderhostel (800/454-5768, www.elderhostel.org [1]), which organizes educational tours for people over 55, offers tours in Memphis [2] and Nashville [3].
For discounts and help with trip planning, try the AARP (800/687-2777, www.aarp.org [4]), which offers a full-service travel agency, trip insurance, a motor club, and AARP Passport program, which provides you with senior discounts for hotels, car rentals, and other things.
Persons over 55 should always check for a senior citizen discount. Most attractions and some hotels and restaurants have special pricing for senior citizens.
Links:
[1] http://www.elderhostel.org
[2] http://www.moon.com/destinations/tennessee/memphis
[3] http://www.moon.com/destinations/tennessee/nashville
[4] http://www.aarp.org