Online Demos

Speed of Sound Calculator.  Calculates the speed of sound given a particular input and relative humidity with a standard atmospheric pressure.
   http://www.measure.demon.co.uk/Acoustics_Software/speed.html

3D Hearing Test! Plug in some headphones, click on each of the ears below, and listen to a 3D sound through somebody else's ears.
   http://www.waisman.wisc.edu/hdrl/take_Test.html