Face in Hole is a site that allows you to create photo montages by putting your face in advertisements, on books, on magazine covers, in famous artworks, on the bodies of famous people and much, much more.
Just choose a subject area (from advertising to art to people & celebrities to sports) and then choose the exact scenario in which you'd like to paste your face. You can then either upload an image or take a picture with your webcam.
Once you've saved your photo, you can share it with friends or use it as your picture on your MySpace, Facebook or blog. The site requires that you have the Flash plug-in in order to work correctly.