For a first post, I can't think of a better web site than this. TED (which stands for Technology, Entertainment, Design) is a yearly conference which gathers some of the world's leading professionals in various fields to present eighteen minute lectures on topics ranging from behavioral economics to art to linguistics.
All these presentations, which they call TEDtalks, are available for free online. As of today, they have over two hundred and a new one is added every week.
My favorites include Dan Dennett's "Cute, Sweet, Sexy, and Funny," Dan Ariely's "Buggy Moral Code," and Robert Ballard's "Exploring the Oceans."