Photojojo covers the issue of getting that great holiday shot without all those other pesky tourists in the photo. They link to three different methods for you to try.
Travelling a lot this is something that often plagues me and I often end up waiting for quite a long time for that perfect shot with either no tourists in the frame or only those I know I can clone out. However the first option listed on this tutorial is one I’ve heard of before. Basically, take multiple exposures of the same scene and as people move about you’ll end up with a series of shots that when combined allow you to pick just the tourist free parts of the photo for a final single clean shot.
To see this method in more detail and the two others they recommend, visit the Photojojo website.