This is an online music dictionary that is easy to navigate, uses examples, and is hyperlinked in each definition.

This is a neat site by Jim Payne that allows students to see some new ideas for funk beats on the trap set. They are written out and can be printed, along with other related information. There are short video/audio tutorials that help demonstrate his beats.

This is a great tool to use with music students of all ages. There are many written trainers (notes, guitar, piano, scales, etc.) and ear trainers (scales, intervals, triads, chords). I use it in class with my high school music theory students (particularly for ear training), and they can access it anywhere to practice.