My elementary principal is a big fan of using Twitter to find educational resources. He passes along good info to different teachers, depending who it relates to. He sent me this a few days ago:
This web page has several links for great online resources for Art and Music.
The art ones are mostly for art history/online art history books, etc. but they are pretty interesting. I got this information at a good time, because my JH kids are going to begin some artist research projects soon, so these sights will be helpful.