Brand Noise, which markets itself as "the blog for brand planners," is an excellent site on news of marketing in all its manifestations. And believe me, marketing has a lot of manifestations.

And here's one I love—

Probably inspired by British graffiti artist Moose, PagesJaunes (the French Yellow Pages) is using «clean-tags», to promote the launch of the 2005 phone books in Paris. The «clean-tags» technique creates graffiti by cleaning dirt from sidewalks, tunnels, walls, etc. They last only one month and have been tagged in metro station.

(See link for photo of sidewalk ad.)

I have an automobile that's dirty enough to make a great canvas. Hmmh. I wonder if I can rent ad space.