Check out these links for extra help, or just for fun!

Learning
​musictheory.net - Useful music theory lessons, exercises, and games.
teoria.com - Another useful theory practice resource
Performance Tips for Young Musicians - Performing is a learned skill! Read some great tips here.

Music History 
​classicsforkids.com - Learn about classical composers. Full of great resources.
Naxos Records - A good, solid, music dictionary from a highly credible source.
imslp.org - GREAT RESOURCE! Access scans of thousands of public domain music for free.

Creativity
blanksheetmusic.net - Design and print off customized blank staff paper.
Note Flight - Free, online music notation software.