flight
ThinkQuest
Aeronautics Learning Lab
Invertebrate Flight
http://www.ucmp.berkeley.edu/vertebrates/flight/enter.html
San Diego Air and Flight Museum
http://www.sandiegoairandspace.org/
Smithsonian Air and Space Museum
PBS Science of Hot Air Ballooning
http://www.pbs.org/wgbh/nova/balloon/science/
How to make paper airplanes