For Kids (specifically rotorcraft)

K - 4: Robin Whirlybird 5-8: Future Flight Design

For Non-technical Teens & Adults
(helicopters - non-NASA!)

http://www.howstuffworks.com/helicopter.htm http://www.helis.com/howflies/

NASA/Army Rotorcraft Research websites:

Rotorcraft Division Aeromechanics Branch Flight Control & Cockpit Integration Branch Army Aeroflightdynamics

Other cool Kids' sites
AIAA Kid's Page
FAA Kids Corner

Snowflake
Helicopter
Pin Wheel
Whirly Twirly