Imprimatur, by American media artist Andy Deck, is a free tool for producing posters.
You can create or contribute to poster layouts via your web browser, print them, and place them strategically in the city. Then you can photograph the posters in situ and upload them to the website.
If you save a poster, data will be sent to the server and your document will be archived for others to see.
Rather than providing images, Deck has chosen to offer a system that invites viewers to activate their own expressiveness, pick up themes and select their own messages. It propels on-line expression out of the ink jet and into the streets.