Waves transport energy without transporting matter. The introductory presentation has a bunch of animations and interactive elements that don't work in the pdf version. If you have the Smartboard Notebook software on your computer, you can download the actual presentation that I used in class.
The string demo is really good for seeing how waves work. You can explore how waves reflect against boundaries, how they experience constructive and destructive interference, periodic waves, standing waves, and more.
These animations are from the introductory presentation on waves. They show transverse and longitudinal waves, and standing waves. The surf movie doesn't have much to do with physics, but there are some cool waves.
The first half of this presentation reviews wave superposition, standing waves, and reflection of waves off of different boundaries. The second half of the presentation is on the Doppler effect and shock waves. You can download the actual presentation, or you can just look at the various animations from the presentation.
You can listen to destructive interference. Play this sound on stereo speakers, then move back and forth between the speakers. You can hear the sound getting louder (constructive interference) and quieter (destructive interference).
Here is a video about waves. It covers lots of material about waves, sound, and light.
Student written web pages:
Wave Properties (AS)
Wave Behavior (MC)