I found this site a few days ago. Delicate Situations - From the blog:
Delicate Situations is a year-long exhibition from 15th January 2007 to 15th January 2008 bringing together work that will be placed in any space anywhere. The one common factor is that all the works in the exhibition are left in a place (for as long as they last).
The works that are exhibited are small, almost incidental. The documentation is as much the art as the installations. One of the ones that I found most notable was King of Cards. (Pictured below) The work was installed and documented by Joe Schneider who is the driving force behind the online exhibit.
Most of the works are ephemeral, lasting only as long as the wind will let them. And some don't seem to have a sense of deliberation. Definitely worth checking out.