Recently, one corespondent suggested that I define libertarianism. I pointed out that it wasn't my job, that there are tons of people who are professional libertarians who could do it, and have done so.
But I've been rather dissatisfied with the definitions I've seen: usually they are written by people who have drunk the cool-ade so long that they're unaware of their own biases. And usually they focus on only a small part of the libertarian spectrum.
I stumbled upon Karl Widerquist's encyclopedia description of libertarianism, and was very pleased with its thorough and evenhanded descriptions of left, right, and socialist libertarianism.
I've added this one to the So You Want To Discuss Libertarianism.... index at my site.