I ran across this at Chosha's blog. There are a lot of these things floating around, but this one was quick and easy, and the questions covered a nice range of subjects. In addition to plotting you on the familiar social/economic graph, you can compare your answers to each question with each candidate's answers as derived from their stated positions, and link to the quotes and other evidence used to support it.
I was a little surprised that by their reckoning, Clinton is farther to the economic left than either Edwards or Obama. I was not surprised that I ended up as a socialist libertine.