Violin Essentials

Rosin
Cleaning Cloth
Music Stand
Metronome
Shoulder Rest
Binder (for lessons)
Tuner

All of these can be purchased from local luthiers / string music stores, or online.

Sheet Music

You can find a lot of your music on the Internet Music Score Library Project. Just download and print.

If you can't find it online, or you want a more permanent, bound copy of something, you can find scores at Shar Music and Sheetmusicplus.

Your violin and bow

Rhythmic note values

Learn your Music Theory!

http://datadragon.com/education/reading/

You can also find theory apps for your smartphone here:
http://appadvice.com/appguides/show/music-theory-apps

Study for the more advanced student

Ivan Galamian's Principles of Violin Playing and Teaching is essential reading for the more advanced player, or any student wishing to pursue the violin more seriously.

The Art of Violin is also highly recommended viewing. You'll learn about the history, great performers, and philosophy behind the art of violin practice and performance from the viewpoint and narratives of internationally renown artists.

Other Fun Links

http://www.creatingmusic.com/
http://sfskids.org/templates/splash.asp
http://www.dsokids.com/
http://www.nyphilkids.org/main.phtml?
http://www.kidtastic.com/city/musiccenter/musiccenter.html
http://www.titlemax.com/songs-to-sing-in-the-car-for-kids/

http://www.theviolinsite.com/violin-facts.html
http://www.violinist.com/
http://www.derekroberts.co.uk/making/