the idea of a distinctively libertarian ideology, neither left nor right, is probably no more than fifty years old.
Libertarian is largely just a more extreme, less left and more right leaning version of what's called liberal in Europe, isn't it? Liberal parties go back quite a bit longer than fifty years.
How useful are "left" and "right" or "liberal" and "conservative" anyway? The folks over at the Political Compass suggest that while most mainstream political figures fall in a line with strong correlation between their views on social and economic issues, there are still substantial exceptions.
See, for instance, this chart dealing with candidates in the 2008 U.S. elections. Draw a line from Dennis Kucinich to Tom Tancredo and you have the U.S. political mainstream represented almost entirely on a single continuum. ...
Jonathan Haidt, a professor at UVA, runs an online lab with quizzes that will compare your moral values to the rest of the population. I have found the test results useful for avoiding the typical mind fallacy. When someone disagrees with me on a belief/opinion I feel certain about, it's often difficult to tease apart how much of this disagreement stems from them not "getting it", and how much stems from them having a different fundamental value system. One of the tests alerted me that I am an outlier in certain aspects of how I judge morality (green = me; blue = liberals; red = conservatives):
Another benefit of these quizzes is that they can point out potential blind spots. For example, one quiz asks for opinions about punishment for crimes. If I discover I'm an outlier w.r.t. the population, I should reconsider whether my opinions are based on solid evidence (or did I see one study that found tit-for-tat punishment effective in a certain context, and take that as gospel?).
Extra reading: Haidt wrote a WSJ article last month that applied the learnings of these moral quizzes to better understanding the Tea Party.