I follow Laughing Squid on Twitter.
Clicking a link from Laughing Squid, regarding Improv Everywhere, one of the coolest, most interactive ongoing art experiments out there, I found another separate link to a very cool Grafitti Report card, downloadable in PDF form, it is designed by Brandon Thomas Baunach of Design Crack. Just download and apply to any wall w/grafitti and fill in your comments... fun! Fun!
Baunach's Grafitti Report Card was inspired by Drew Heffron who designed Grafitti Critique, a harsher, more comprehensive response to grafitti art. Drew's Grafitti report card doesn't seem to be available for download anymore...
However, Drew's site led me to the very facinating Yellow Arrow Project!