ONLINE THEORY WEBSITES
In Lessons Ms. Isabelle uses theory games from Michiko Yurko's method, Music Mind Games. You can see more about Michiko and the games, and can purchase materials here:
Online theory games: http://www.themightymaestro.com
- go to "Free Section" and "Get a free login"
complete math problem, click "Check Answer"
Click "Canada, US"
then, "PLAY NOW"
Online musical exploration: http://www.sphinxkids.org/index.html
Kids Music Website: http://listeningadventures.carnegiehall.org/index.aspx
MUSIC THEORY APPS
Violin Notes Flash Cards
Music Theory for Beginners
Music Theory Pro, Joel Clifft
Music Theory, with AUDIO
A great way to practice music theory (note names, symbol recognition, note values) is to use flashcards. You can order violin or viola theory flashcards online or find them at most music stores.
Besides flashcards I highly recommend taking choir if at all possible! Learning to sing and read choral literature is excellent training for violinists.