If you are a geek, designer or enjoy science and you want to hear great presentations from some of the great thinkers and doers. I think you will find TED( Technology, Entertainment, Design ) an enjoyable site to hear them speak. Each speaker has 18 mins to give a provocative speech in their area of expertise.
Below are a few that I really enjoyed.
Talks Yochai Benkler: Open-source economics
Yochai Benkler explains how collaborative projects like Wikipedia and Linux represent the next stage of human organization.
Talks Ray Kurzweil: How technology's accelerating power will transform us
Inventor, entrepreneur and visionary Ray Kurzweil explains in abundant, grounded detail why, by the 2020s, we will have reverse-engineered the human brain and nanobots will be operating your consciousness.