The political spectrum -- left to right, if you like -- is a hard thing to define.
As Craig points out, the dominant parties in western countries since WWII might better be classified as "center-left" (here, democrats) or "center-right" (here, republicans). As a political moderate, I view that as an excellent thing.
I think of the "center" part of their designations as meaning they agree on several basic principles:
1. Democracy as the basic form of government.
2. Free market capitalism as the basic economic system. We can fight about how much regulation to apply to those markets, but nobody's saying capitalism sucks.
3. Agreement that government owes certain things to its citizens: protection (national defense) and some form of social safety net. We can fight about how big the size of the safety net and the defense budgets, but not whether they should exist at all.
4. Respect for individual rights, especially the opposition's rights. We can debate how extreme the freedom of speech should be (can I yell "fire" in a crowded theater? what constitutes liable? etc), but not whether or not the freedom of speech exists.
Craig, the reason I don't think you should label Republicans as Fascists or Nazis is because unlike those groups, they endorse the principles above. Like it or not, in my books you're also only "center-left," unless you advocate some position I'm not aware of that would outlaw one or more of the above principles.
Had to give you a thumbs down Chris. Capitalism does suck. The fact is you don't have the freedom to do anything important. Suppose I want free medical care?? How would I do that?? Suppose I want a party that stands up to the rich?? How would I get that??