The annual Azalea Festival in Valdosta, Georgia includes a century bike ride as well. This is the fourth year, I believe, that the century has been organized and it keeps getting better and better. The temperatures are usually very nice, which makes for a great ride. For more information, please visit the Azalea City Cyclists webpage on the ride:

http://www.azaleacitycyclists.com/bikeride.htm

For more information on the Azalea Festival, please visit:

http://www.azaleafestival.com/