This website allows you to match your opinions on a series of issues with the candidate who most closely agrees with your views. The questions don't allow for nuance, but it's nevertheless an interesting guide.
One caveat: When you click on the button to see which candidate matches your responses it may show you the candidate who is least compatible with you. If so, just scroll to the top of the page. I was shocked when I clicked on the button and Chris Dodd's picture came up, but then I scrolled to the top and there was ..... Fred Thompson. Unfortunately, Mr. Thompson will probably no longer be a candidate after his disappointing showing on Saturday in South Carolina.
Thanks to Scott S. for the link.RLC