This site has some awesome games to train your ear. Some have you practice tuning by matching pitch, another tests your ability to focus on hearing a specific instrument and guessing which one is being highlighted.
Here are instructions on how to make your own string instrument at home! If you decide to make this, you can pretend it's a violin and use it to practice proper playing position!
This site has a bunch of games related to reading music and learning piano (which can help a lot with violin. All of these games do require AdobeFlash so you'll need to download that first.
This site has some more fun games and readings about composers and instruments. This site also requires a flashplayer which is provides a download for on the website.
Some more games about composers and instruments. Including games specific to learning a scale, Beethoven, and creating your own music. This also requires AdobeFlash player.
Here is a site that is specifically for reading music on the staff. The game at the beginning does not require you to download anything or to add it to the home screen. To go from page to page, click on the little pianist in the corners of the screen.