No list of great contemporary business speakers would be complete without Seth Godin.  You can see him here, talking about marketing to Google a few years ago: http://tinyurl.com/nswcwx.  

Seth has an extraordinary ability to take complex topics and break them down, explain them clearly, and make them appear simple.  That’s the essence of great marketing, and it’s why so many of Seth’s books have been bestsellers, from The Purple Cow http://tinyurl.com/m3scm8 to Tribes http://tinyurl.com/nltgt9. 

As a speaker, Seth has the persona of an approachable, down-to-earth academic, very smart and savvy.  He’s a gifted teacher, in short, and his strength is the strength of all such individuals – a passion for transmitting his clear understanding of a topic into the minds of his listeners.  A classic example is his talk on TED about how to market in an era of too many choices:  figure out who cares and offer them something remarkable – i.e. a purple cow.  http://tinyurl.com/aeuaf9.  The talk is from 2003 and feels a bit dated in our current economic moment, but the ideas are still as powerful as ever.  They’ll come back when the market does.  In the meantime, check out Seth’s blog, which is brilliantly shaped for modern readers on the go (http://sethgodin.typepad.com/).  It always limits itself to one idea, makes the point quickly, and moves on.  Many blogs, and speakers, could benefit from Godin’s economy, simplicity, and style.