North Carolina has some of these...Quilt Trails is the newsletter. Don't recall the name of the project, but they have a website. I saw it the first time 2 years ago, and they now have over 100 quilt blocks on buildings in the area. It is in the mountains in Western NC.
Edit - Here's the link:
http://www.quilttrailswnc.org/ My daughter lives in Spruce Pine, NC, and we took a day trip to see the quilt blocks. We got about 20 or so pictures of them.