Under this schematic, 34 percent of the country self-identifies as 'conservative', 29 percent as 'moderate', 15 percent as 'liberal', 16 percent as 'progressive', and 2 percent as 'libertarian'.
After moderates are asked which approach they lean towards, the overall ideological breakdown of the country divides into fairly neat left and right groupings with 47 percent of Americans identifying as progressive or liberal and 48 percent as conservative or libertarian and the rest unsure.
Labeling aside, Americans lean toward the left in their policy preferences. The ThinkProgress interactive quiz is interesting, as is the scoring. Here is my score, followed by the aggregated results:
Chris Bowers has some good commentary at OpenLeft, calling the quiz "pretty decent" while recognizing "problems with a few of the questions." With a score of 361, he's more of a bleeding-heart than I am. I wonder what they call the category comes after "extremely progressive," but I'm not going to take the quiz again to find out.