In Toronto in the 80s there was a street artist who bolted lacquered and painted books to public places (lamp posts, chain link fences around parking lots, etc.). I lived in the downtown area and was always happy and amazed to come across these pieces unexpectedly. The works were definitely site-specific with the image content subversively appropriate to their location. Unfortunately it never occurred to me to take photographs at the time. I do remember though that the pieces were noticed by the powers-that-be in the city; since property would be destroyed by cutting the bolts to remove the books, the decision was made to send a worker out to paint all the artworks white...At least one was missed near where I lived on Queen St. West, as it was bolted near ground level, and could only be noticed if, say, you were crawling home along the pavement (not that strange an idea at Queen & Bathurst in 1988).
From 2009 to 2012 I (and various friends & members of family) engaged in the stickering project Placement© in which small stickers with images of my artistic oeuvre were surreptitiously placed at locations around the world. Cities such as New York, London, Toronto, Chicago, and Prague got their fair share of Placement© stickers.
But other locations included a ski chair lift in Lake Tahoe, USA
and overlooking the Mediterranean Sea at Antibes, France.
Quite a few placements were also made in smaller towns and rural areas of Ireland as well as unusual places on airplanes! For more information on Placement© look here.