I've read a few articles about yarn bombing as a Knitter's form of graffiti. This bus is the most recent one I came across
You can read the article here http://www.telegraph.co.uk/news/uknews/4305406/Knitters-turn-to-graffiti-artists-with-yarnbombing.html
I don't want to ever knit something like this myself but I love it!
If you want to see more you can take a look at this blog as well http://yarnbombing.com/