I just finished watching Thomas Barnett's talk from PopTech! I like reading Barnett, but watching him is another thing altogether. He's a very good presenter and very entertaining. If you want a gentle introduction, watch the video. I don't think the audio would do this talk justice.
There are some other talks on that page that look pretty interesting. Friedman is always good--I had breakfast with him one day at the Governor's mansion when I was Utah's CIO. I heard Juan Enriquez at the Governor's mansion during the Olympics and read his then new book, As the Future Catches You. His latest is a look at a possible future of the US.
Sometime I'd like to have a relaxed conversation with Barnett. I think he'd be very interesting to just hang with for a bit. That's maybe one of the best, overlooked perks of being governor: the convening power that allows you to spend time with interesting folks and learn from them.