In case you haven't seen this before, Ji Lee's "The Bubble Project" is (was?) one of my favorite street art projects in NYC (see links below)

Ji Lee's "The Bubble Project":

 

pleaseenjoy.com/project.php?cat=1&subcat=&pid=3&a...

 

thebubbleproject.com/

 

Also great (and I found this while searching for Bubble Project links):

 

mrod.wordpress.com/2009/01/18/thought-bubble-street-art/

Done