The above link lets you measure the distance between any two points on the globe using a number of different references, such as place names or latitude and longitude (which you can get from sites like http://www.streetmap.co.uk/). I suppose it isn't much of a surprise such a service is available on the web. But what is cool is that it's hosted in Bali 7770 miles from London.
Another interesting tidbit… If you accidentally type http://www.streemap.co.uk instead of http://www.streetmap.co.uk you get "Hanky Panky College" which is surprisingly different from StreetMap and seems to have nothing to do with cartography.