from The Physics Classroom Tutorial, at Glenbrook South High School in Glenview, IL.

http://www.glenbrook.k12.il.us
/gbssci/phys/Class/waves
/u10l1a.html

Originally written for high school physics students by Tom Henderson, science teacher at Glenbrook South High School. A good introduction to wavemotion with checking questions, animations, graphs, etc. to help the student understand wave motion.

from the ExploreScience site of Raman Pfaff at the University of Michigan, Ann Arbor.

http://www.explorescience.com
/activities/activity_list.cfm?
categoryID=3

In order to use this site you must download and install the Macromedia Shockwave Plug-in on your computer.

These activities -- Sound Pulses, Sonic Doppler Effect and Two Source Doppler Effect all display animated sonic phenomena and allow you to manipulate variables and make onscreen measurements.

by Dan Russell, at Kettering University in Flint, MI .

http://www.kettering.edu
/~drussell/Demos/waves
/wavemotion.html

One of many excellent animations at Russell's Acoustics and Vibration Animations. This page shows animated gifs of mechanical waves propagate through a material medium. Particle motion for Longitudinal, Transverse, Water and Rayleigh Surface Waves are modeled.

These sites discuss the speed of sound in a air and other gases.
The speed of sound in a gas depends upon:

Temperature:http://hyperphysics.phy-astr.gsu
.edu/hbase/sound/souspe.html

Humidity:http://www.measure.demon.co.uk
/Acoustics_Software/speed.html

Altitude:http://www.grc.nasa.gov/
WWW/K-12/airplane/sound.html

Type of Gas:http://hyperphysics.phy-astr
.gsu.edu/hbase/sound/souspe3.html#c1

HyperPhysics by C.R. Nave at the University of Gerogia has some other notes on waves as well as the two calculators above.