Chiasmus.com
Chiasmus is "a reversal in the order of words in two otherwise parallel phrases." Dr. Mardy Grothe collects exemplars of the art. We especially like this one, relayed by John F. Kennedy in 1956: http://www.chiasmus.com/mastersofchiasmus/kennedy.shtml
Source: http://www.chiasmus.com/
Categories: Traditional and Exotic Verse Forms