Kurt Wenner is an American artist that lived in Europe during the early eighties, and claims to have invented anamorphic street painting in 1984. This is not typical chalk art, but are intended to be viewed from a particular perspective and there trick the eye into seeing a 3-D image. His images are impressive.
There are a couple German artists who have followed with similar success. I've never seen these people or their work in person, but I really hope to.
First is Edgar Mueller, from Muelheim. His website claims "Since 1998 Edgar Müller has held the title of 'maestro madonnari' (master street painter), born by only a few artists worldwide. The title is awarded at the world’s largest street painting festival, called The Grazie Festival, which is held in the small pilgrim town of Grazie in Italy."
He too travels to festivals and competitions, like what he did in Geldern, Germany:
Cool how he uses real people to enhance the effect.
The second guy is Manfred Stader. He studiet art in Frankfurt and is now freelance - his web site makes it clear that you can even hire him to create 3-D street art at your festival/event/etc. He did this in Hong Kong for a conference:
What is just as cool is seeing a time-lapse video that shows the "making of" art like this. Here is a video from Edgar Mueller. You can see the team mapping out the lines of perspective at the start:
Edgar and Manfred both have many more pictures on their personal sites, and Manfred has videos too. Hopefully Frau A and I run into one of them this Summer.