The political spectrum is pretty much irrelevant. It should be a scale from those who want the least restrictions on human liberty to those who want the most.
So basically, it would go from left to right:
Anarchism - Libertarianism - Socialism - Conservatism - Authoritarianism
So centrists don't count?
Not a clear enough term. You could have called me a centrist a year ago, when I was pro-temperance.
Well you have centrists in the left-right spectrum, even though it's not any clearer there.
That aside, if you are talking strictly about social liberty, then there are two main currents there. Anarchists, libertarians, & socialists mainly clash on the notion of positive liberty, though the social views of socialists need not be as clearly pigeonholed. Conservatives & authoritarians function well as a continuum, actually.
If you are also talking about economic liberty, it is not altogether clear that socialists should be to the left of conservatives, since socialists support far more regulation & public ownership of industries.