Here's a very nicely done overview of the physics of sound "by students and for students" at think quest.org. Great illustrations of the concepts.
Here's one that's not too exhilarating, but a well written overview nevertheless. Covers things like diffraction, refraction, standing waves, etc.
"The Nature of Sound" with special emphasis on natural sounds, whales, birds, etc.
Good illustrations and examples.
Sonic boom explanation and recordings
More on sonic booms