Recently I discovered Art Babble
Similar to 'youtube' it's a collaborative project with a number of institutional partners, including Art21, Indianapolis Museum of Art, Los Angeles County Museum of Art, MoMA - The Museum of Modern Art, San Francisco Museum of Modern Art, Smithsonian American Art Museum, and New York Public Library.
The site also provides venues for user comments and contributions.
noun; verb (used without object) -bled, -bling
1. free flowing conversation, about art, for anyone.
2. a place where everyone is invited to join an open, ongoing discussion - no art degree required.
ArtBabble was conceived, initiated, designed, built, sculpted, programmed, shot, edited, painted and launched by a cross-departmental collection of individuals at the Indianapolis Museum of Art (IMA). It is intended to showcase video art content in high quality format from a variety of sources and perspectives.
ArtBabble was created so others will join in spreading the world of art through video.
Some might find that site interesting, too.