Channel 4 (UK) has launched a very cool site where you can take pix with your mobile phone of public art and send them to their server. They are then located on a map. This is an excellent use of locative media, the ubiquity of the camera and social networking.

At the moment most mapped public artworks  are in the UK, then Europe and a few in the US. Would be great to see some Australians posting works there. You can upload via a pc as well. Someone really should take a photo of whatever currently is decorating Taylor Square in Sydney!