Interesting graf site that uses various photographs to create time-lapse collages of walls, tunnels and other popular canvas’ that were hit up by writers over time. Link (requires flash), via webbyawards

“Graffiti Archaeology is the study of graffiti-covered walls as they change over time. The grafarc.org project is a timelapse collage, made of photos of San Francisco graffiti taken by many different photographers from 1998 to the present….Using the grafarc explorer, you can visit some of San Francisco’s classic spots, see what they looked like in the past, and explore how they have changed over the years.”