Joe Stewart put together a great little page that leverages the feature of Conficker that blocks certain websites. I've mirrored that content here to save Joe some bandwidth.
The page is really simple in that it loads images from the different websites. If you're infected, you'll see images missing. He has included a chart on how to determine what you might be infected with. If you are infected, check out the Internet Storm Center's page full of links on how to get cleaned up.