Hi Andrea, we have been talking about having one of those 'clings' made for the back window of our car - I think I'd rather use something that I can remove if need be and bumper stickers are so small... Even a car door magnet I think would be better in terms of impact than a sticker.
Bernice is right - do check out the
SEO section for ideas to increase his organic traffic. Otherwise, all of the usual things apply in terms of creating great, dynamic content on his site. Does he blog?