It’s hard to quantify political beliefs, but of anything I’ve seen the Political Compass does a pretty good job. Eschewing the vague left-right paradigm, it adds a third dimension: authoritarian/libertarian. The test presents to you a large number of statements from six different categories and asks you to rate the extent to which you agree with them. Examples include “I’d always support my country, whether it was right or wrong” and “the rich are too highly taxed”. At the end, it generates a graph for you.
I first did the test about five years ago, and I was really surprised to see that I’ve since then moved further left and down – I really thought that I’d mellowed in a lot of leftist views. Maybe my ideas of it are different to the creators of the test (and I’m sure theirs are more correct seeing I’ve never really done any in-depth political science study.)
They also have reference graphs (approximated, obviously) of the main candidates of the 2008 US Primaries and the Australian political parties. Depressingly, they’re generally all very far from the green quadrant – maybe this is because their scores are based on actions and not just beliefs. I’m sure mine would look a bit different if I had to make practical decisions everyday and not just hold ideals.