I've been using this for a week, and it's great!
Track Me Not is a little Firefox add-on that can foil the search engines' efforts to profile you when they track your search terms. You don't even need to be paranoid to see the benefits of hiding your actual search input in a cloud of noise. The search term being used by Track Me Not at the moment is always visible in the lower right corner of the Firefox frame.
TrackMeNot is a lightweight browser extension that helps protect web searchers from surveillance and data-profiling by search engines. It does so not by means of concealment or encryption (i.e.covering one's tracks), but instead, paradoxically, by the opposite strategy: noise and obfuscation. With TrackMeNot, actual web searches, lost in a cloud of false leads, are essentially hidden in plain view. User-installed TrackMeNot works with the Firefox Browser and popular search engines (AOL, Yahoo!, Google, and MSN) and requires no 3rd-party servers or services.
Terms used by the little bot tend to be pretty innocuous: "Ashlee Simpson", "France", and "city slickers", for example. They are nothing like I would ever use, so a clever analyst might be able to find my searches like a bowling pin in a haystack: "installing Skype in Ubuntu", "killing Microsoft", "Glitter & Doom -- portraiture of the Weimar Republic". But, not wanting to leave it to Google and the others, I feel that my privacy is quite substantially more intact, now.