The graffiti in Brazil was fascinating. There were a number of derelict looking buildings that had graffiti all over them. I kept staring at them, trying to figure out how they managed to tag them.
The freeway and other public spaces also had some really interesting graffiti. There was one underpass that had some really exceptional ones but we drove by too quickly to capture.
Take a look at Brazil Graffiti: http://www.flickr.com/photos/tristanmanco/sets/154564/