Sound, Pitch, Dynamics and Tone Color
http://www.muc.edu/~miskeljp/intro/Materials/Materials.html
Here is a helpful online appendix of many terms associated with sound, pitch, dynamics, and tone color. The site contains sound file musical examples of key terms, which can be uploaded. Additionally, examples of basic rhythmic concepts, including syncopation, are playable from the screen.

Another valuable resource related to this site is
http://www.muc.edu/~miskeljp/intro/kamien/1/1.htm.
This Appendix provides examples and definitions for key terms related to the elements of music.

The Physics Classroom
http://www.glenbrook.k12.il.us/gbssci/phys/Class/sound/u11l2a.html
Sound theory and human sound perception are succinctly presented at this site, with simple animations easily readable from most browsers.

Musical Elements
http://www.wmich.edu/mus-gened/mus152/Elements/sld001.htm
This site is a PowerPoint slide show on musical elements by Dr. Daniel Jacobson of Western Michigan University

Table of musical pitch
http://www.music.vt.edu/musicdictionary/appendix/pitch/pitch.html

Musical instrument pitch ranges
http://educ.queensu.ca/~fmc/november2002/hMusicalPitch.html

Notation of musical dynamics
http://www.bbc.co.uk/schools/gcsebitesize/music/musicalelements/notationrev8.shtml

Notation of rhythms
http://www.bbc.co.uk/schools/gcsebitesize/music/musicalelements/notationrev6.shtml

Rhythm and meter
http://library.thinkquest.org/16020/data/eng/text/education/theory/rythm.html

The physics of musical tone and timbre
http://www.commodore.ca/manuals/128_system_guide/sect-07b.htm