Balloon Vine, a non-native and potentially invasive species, has been added to the USWildflowers database (09/27/2010.)  Scientific name is Cardiospermum halicacabum.  It’s also known by the common names Love in a Puff and Heartseed.  Photo below was taken at Reflection Riding in Hamilton County, TN on Sep 5, 2010.

Balloon Vine, Love in a Puff, Heartseed - Cardiospermum halicacabum