graffiti archaeology <grafarc.org> is an awesome project that a friend, cassidy, has been toying with, on-and-off, for quite some time now. if you are a fan of graffiti, its definitely worth checking out.
it requires flash 6, and has a great interface to browse graffiti progress over time by "peeling back" layers of art (and attempts to stop it!). also cool is the fact that the source images for the art sites came from all sorts of contributors, so its great to note the collaborative nature of the website as well.
Active/New discussions on SITO have been moved to Google Groups.