I just found this homepage with some really cool 3D-art drawings drawn right on the pavement by the artist Julian Beever, aka the Pavement Picasso.

Julian Beever is an English, Belgium-based chalk artist who creates chalk drawings on pavement that create the illusion of three dimensions when viewed from the right location. These trompe-l’oeil drawings are created using a projection called anamorphism and appear to defy the laws of perspective.

I also found some really cool street paintings by Kurt Wenner at his homepage.