New from the Cato Institute, Libertarianism.org, a resource on the theory and history of liberty. From the opening page introduction:
Liberty. It's a simple idea, but it's also the linchpin of a complex system of values and practices: justice, prosperity, responsibility, toleration, cooperation, and peace. Many people believe that liberty is the core political value of modern civilization itself, the one that gives substance and form to all the other values of social life. They're called libertarians.
The site has essays and a blog and videos of people like F.A. Hayek, Milton Friedman, Murray Rothbard and Joan Kennedy Taylor. Check out the essay on the history of libertarianism.