The excellent "Celebrity Series of Boston Blog" posted an interesting bit about pianos being "deployed" about the street corners of London.
Details and more found here.
Now what would be interesting if these setup sort of like the NPR story booths, so that just anyone could walk up to one play something and have it recorded. Oh sure, you'd have to wade thru alot of chopsticks, fur elise, and so one. But you know there'd be a nugget or two that'd make it all worth. Just like gold panning. Call is "sound panning"... Or something.