In the UK the Tate Liverpool museum has launched a digital action to let visitors share their thoughts and feeling around the art pieces in its collection. It's an interesting project, first of all because it's a rare example of online art marketing. I'm definitely not an art expert, but I feel the insight and the idea of opening up art world (and the artworks) to the public are a very fertile field.
The website created by Fallon London is definitely very 2.0, not just because it features the "traditional" tag cloud but because it stimulates users' participation. There is only one thing I find a bit weak is interface, which results a bit too clean and simple even empty I would say.