When I go to someone's page of Flickr friends, I'd love to be able to see who we have in common. (This is a feature that I wish a lot of sites had, but I thought of it again tonight while browsing some Flickr photos.)
Just wanted to make a note of that before I moved on to another task.
Have you checked out mybloglog? - they are starting to integrate some flickr features since the acquisition. Don't think flickr is going to allow outside widgets though.