www.googleartproject.com I really recommend checking out. It is like google earth but in museum format the kids love it.
The FAQ page for questions:
GO to youtube and you can find all sorts of video from each museum.
My favorite is before I introduce a museum I show them the quick overview video. Such as if I going to go over art pieces from the MET I will show them this video and then get into the art from the MET.
I love t be able to zoom in and show them the texture, a lot closer than if I was actually at the museum without setting off the alarms. Also I like how I can show the students where it is in the museum and I love the media tab if they have a video clip about it.