Damn good job there's another long weekend coming up, because here's a web site that will have you playing for hours. London Low Life from AxisMaps collects together almost 30 historical maps of London and superimposes them over a modern Open Street Map.
The interface is simple and familiar. Drag the maps around and zoom in using a sliding scale. A second bar lets you adjust the opacity of the older map, allowing a gradual fade-in/fade-out between the two eras.
And that's just for cartographic starters. Another tab explores themes in Victorian London. Find the locations of the city's hospitals, universities, lunatic asylums and more, with a sliding scale that lets you move through the decades. Another tab offers something akin to Street View, with clickable map markers bringing up 19th century etchings of shop fronts all over town. A final area presents old photos and descriptions.
With so many maps to choose from, ranging from the late 18th Century to the early 20th, this is an essential resource for anyone researching the period. For everyone else, it's a fascinating way to explore the recent history of the city.
Those with iPhones and iPads may enjoy a similar product that uses a touch interface to let you zoom through the ages. Time Travel Explorer also allows fading between old and new maps, but goes back a little further, to the 1740s. The app also includes an audio guide to historic London and many images. (Disclaimer: Time Travel Explorer was developed by Londonist's sister company LDN Creative.)