This map superimposes Google maps and Victorian Ordnance survey maps of London circa 1893-1896. I've already found some interesting surprises including a row of houses across the road from my house that was demolished to make room for railway lines some time between then and the 1940s.
Update - I posted this to the little_details comm and got several more recommendations:
1746 and 1869-80 surveys
Scotland (and the rest of the UK) - lots of different maps
Aerial images, 1919-1953: