Marketing blogs

Seth Godin
Guy Kawasaki
John Carlton
Gary Halbert
Bob Bly [direct marketing]
Jason Calacanis
Jennifer Slegg [contextual advertising]
Josh Greene
Tom Peters
Neville Medhora
Darren Rowse [website marketing]
Perry Marshall [google adwords, guerilla marketing]
Bob Parsons (GoDaddy.com owner)
Donald Trump
MIT Advertising Lab
Trend Watching
Adverblog
The Advertising Show [podcasting]
Marketing Experiments