What is neoprene made of?

Neoprene is a commercial material made of different combinations of materials depending on which type of neoprene you are talking about.

More info here:
Neoprene - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Neoprene)
Neoprene (http://www.dupontelastomers.com/Products/neoprene/neoprene.asp?id=wikineo)