I have often linked to a 2005 Pew Research study that groups Americans politically according to factor analysis rather than direct questioning of ideology. It has been an interesting contrast to the usual red/blue/green political assignments in the media.
Now there is a new version. I have only glanced at it thus far, but expect the comparison to the 2005 version will be interesting.
Update: I should mention that I am aware of the large methodological difficulty with the Pew polls. They are telephone polls, with a low response rate. It may well be that a few of these categories have, for some reason, a high percentage of people who really like answering these things, while other categories contain those who refuse to participate at a higher level than the general population. So hold the numbers very lightly in your head while making comparisons. It is useful more as general guide to the attitudes and ideas that seem to associate with each other.