English Heritage maintains this wonderful interactive map of all listed buildings in England. London is peppered with thousands of historic properties, including many unexpected entries in residential areas. Is there a listed address down your street?
The map also shows the extent of our four World Heritage Sites (Greenwich, Tower, Kew and Westminster) as well as scheduled ancient monuments, historic parks and EH properties. All locations are backed up with information records. With just 20 seconds tinkering, we found out exactly who paid for the weird cattle trough at the end of our street. The map's a little bit clunky (not surprising, given the sheer number of locations), but the content is superb.