References

This is a list of websites I have found to be useful for the development of musical skills and knowledge:

Music Theory / Ear Training:
http://academic.udayton.edu/tobyrush/theorypages/pdf/complete.pdf
www.good-ear.com
http://musictheory.net/
http://www.practicesightreading.com
http://www.sightreadingpractice.com
www.hooktheory.com

Piano:
http://www.pianonanny.com/

Strings:
http://www.musicopedia.com/
www.guitarlessonworld.com/lessons/lessons.php
www.essentialguitar.com
http://www.chordfind.com/4-string
http://banjochords.net/
www.chordbook.com/guitarchords.php 

Drums:
www.onlinedrummer.com
www.drummerworld.com
www.8notes.com/school/lessons/Percussion/drum_lesson1/drum_lesson1.asp