Seth Godin ranks as one of my favourite authors and thinkers on marketing and media.
Check out his blog at http://sethgodin.typepad.com/
He give’s a lot of his stuff away for free too. Here are a couple of freebies.
Seth Godin’s Free ebook “The IdeaVirus”- http://www.sethgodin.com/ideavirus/downloads/IdeavirusReadandShare.pdf
Seth Godin’s Free Audio book “Tribes” : http://free.bou.me/Tribes-WeNeedYouToLeadUs-FreeVersion-Unabridged.mp3