The LAARC are doing a community excavation at the Michael Faraday School down in Southwark, and they're putting photos and video as they go. I love the way they're using Flickr notes to point out possible features (features are things like walls, ditches or pits). There's also an experimental wiki (http://laarchaeology.wetpaint.com) and some youtube video (http://www.youtube.com/user/LAARCaeologist). Check out the photos at http://flickr.com/photos/laarc/collections/72157600500588102/
Disclosure: I have a vested interest because it's a work project, but I'm also enjoying this way too much not to share it. We've been working with the LAARC (London Archaeological Archive Resource Centre, part of the Museum of London Group) on pilots for increasing user interaction and engagement.