When we talk about street art most of us immediately thinks about graffiti and similar artworks. Graffiti is interesting artistic way, there's no doubt about it, but this is not single way of performing street arts.
The best example for this are artworks of artist Liliwenn who is creating some of the most interesting street artworks. She likes to say that her gallery is everywhere. She paints randomly on old abandoned buildings or street walls. Here you can see some of her street artworks.

Liliwenn's flickr photostream