The Institute for Humane Studies produced a two-minute video featuring Harvard Professor Jeffrey A. Miron.
The video, "What it means to be a libertarian" does an excellent job explaining the difference between libertarians, conservatives, and liberals.
Jeffrey A. Miron is senior lecturer and director of undergraduate studies in economics at Harvard University. He blogs at http://jeffreymiron.com and is the author of Libertarianism, From A to Z.