Okay they may not exactly be the future of aerospace but It seems that bats could be the answer to the future of Micro Air Vehicles, with the US Air Force thinking launching a six million dollar project:

 http://www.flightglobal.com/articles/2007/07/11/215436/usaf-funded-bat-study-could-produce-better-mavs.html

 Bats really are remarkable creatures but you would  have to pay me about 2 million of that six to get anywhere near the little blighters...