I just started using Scour, a search engine that let's you vote and comment on the results.
Scour queries the top 3 major search engines: Google, yahoo and live to provide results so it's like using your preferred search engine with a social twist. You can vote up or down each result and comment on it and then scour uses this data ( votes , comments ) to provide better relevancy.
The problem is that when people want to search they want results quick and once they get them they just leave so in order to encourage users to contribute scour rewards them with points that can be converted in money using visa gift cards.
The idea is that since the major search engines are making billions from search the user should get something ( more then just search results ) out of it too.
Once you signed up to scour you can start using it for your daily search just like you did with google, yahoo or msn . They even have a search bar plugin for internet explorer and firefox and in the faqs you can find instructions about how you can make firefox use it as the default search engine instead of google. There is also a toolbar but apparently it's only for internet explorer or only for windows ( .exe ) .
As you keep searching, voting, commenting you accumulate points. For each search you get 1 point, for each vote you get 2 points and for each comment you get 3 points but a maximum of 4 points / search and once you reach 6500 points you get a $25 visa gift card.
I like Scour both for the ideas of higher relevancy through votes and comments and also for rewarding users.
Scour is still in the beginning and there are some small problems with it like : try searching for : 'var/log' or the fact that it only displays 3 pages of results, but I'm sure they will be fixed and the search engine will improve over time.
Of course the whole idea of better relevancy will work only if more users will sign up , use it regularly and contribute.