Not sure if this experiment is still going on:
http://www.google.com/experimental/a840e102.html
This experiment lets you influence your search experience by adding, moving, and removing search results. When you search for the same keywords again, you'll continue to see those changes. If you later want to revert your changes, you can undo any modifications you've made. Note that this is an experimental feature and may be available for only a few weeks.
http://www.google.com/experimental/a840e102.html