Urban archaeology
I've always been fascinated by relics of a city's recent history - New York's water towers, Johannesburg's mine dumps, London's disused tube stations. The other day, while wandering around London, I thought it would be cool to compile a page of the old, faded advertising signs for long-forgotten products found on the sides of many old buildings. Someone beat me to it. I might still do it, anyway. Remniscent of Kottke's lovely Minneapolis sign project.

Thanks to Groc for pointing me in the direction of Lilek's similar ghost ads section. I still think we need a UK one.