"Liberal" and "libertarian" both derive from liber "free, unrestricted, unimpeded; unbridled, unchecked, licentious." In much of Europe today, "liberal" is associated with free markets, which is associated with conservatism. It can be very confusing, and so I've stopped using the term "liberal" as the general term.
As a technical term, when you're talking among educated people, you can use "liberal," but for a general non-technical sense, I've started using "progressive" to describe myself lately. Another good word is "left" or "left wing", but I think progressive catches the essence of the idea better.
I think unrestricted freedom is sort of a nutty idea, and so the original sense of the root word matches the nutty libertarians better, anyways.