Different modes of sound wave propagation are described in this non-destructive evaluation site.
An excellent site for virtual demonstrations of waves, light, sound, etc. is available through the University of Salford, Manchester, U.K. The link is here:
Ocean waves are "gravity waves," in that the restoring force comes from gravity, not waves of the gravitational force itself, a long-sought phenomenon in physics. The motions in water gravity are more complex than those of strings or sound. This site gives a great discussion of some of the issues, and the complexity of the motions.
Here's a link to an amazing pendulum array video. It shows a series of pendulums with monotonically increasing lengths that are started in phase, and that each oscillate at a different rate. The resulting patterns are fascinating, surprising, and often beautiful.
This is an excellent discussion of error analysis and reporting from Prof. Frank L. H. Wolfs,
Department of Physics and Astronomy, University of Rochester, NY
A set of neat little applets from Walter Fendt. Scroll down to the oscillations and waves section to see simulations of resonance, coupled pendula, beat frequencies, etc.
A set of physics applets from the University of Colorado, including waves, motion, quantum, light, and many others.
A “friction harp” that uses resonance to produce tones. “Tis a Gift to be Simple”
A really nice simple harmonic motion demonstration at CoLoS, Conceptual Learning of Science, showing a revolving circle linked to an oscillating spring. Very clear depiction of displacement, velocity, and acceleration.
Physics demonstration videos from Wake Forest University Dept. of Physics.
A nice video on Einstein's theory of relativity.
And one on visualizing the fourth dimensions, and more.
Michio Kaku on the 11 dimensional branes that string theory postulates.