Seth Godin strikes me as the Yoda of modern marketing. Read this.
He holds a micro-MBA course at his home. The announcement of his first one was one of the first times I heard of him. I remember being amazed that the only real qualification I had (or pre-qualification I inflicted on myself) was that I was within easy commuting distance from him (Hastings, in Westchester County, NY, while I lived in Putnam Valley).
Pencil sketch, scanned and traced into Adobe Illustrator. Some strokes vary in width using the Variable Width feature.