I haven’t looked at the whole site yet but I loved the idea so I wanted to post it while you could still vote (until 20 July 2008):
London Transport Museum is hosting a Flickr scavenger hunt on Sunday 6th July in Covent Garden as part of the events for the London Festival of Architecture 2008. Focusing on the transport network’s quirky design features, in a race against time teams of photographers will have to unlock a series of cryptic clues in order to snap roundels, station murals and much more. Have you got what it takes to get all the shots and make it back to the Museum? Prizes for the first team back (with the most correct answers), and – voted by the public – the best team and the best picture uploaded on Flickr.