An excellent site dedicated to showing the movement of search engine results (in Google) for a set of 1000 keywords.
Search engines are amazing gateways to virtually unlimited content, and at RankPulse our goal is to provide some insights into how they work. One of our primary intentions is to show webmasters that although unscrupulous search engine optimization (SEO) techniques may yield temporary benefits, they are not foundations for a sound and sustainable website.
Note: Search Engine Voodoo is not search engine optimization in the "unscrupulous" sense of the word: my suggestions are about building a better, quality site which is optimized for good search engine rankings. I don't use any techniques that purposefully game the system.