WebMynd is an extremely useful Firefox add-on that embed search results from Flickr, Wikipedia, Backtype (for blog comments), Delicious, Digg, Amazon, LinkedIn and a dozen other custom locations into Google search pages.
It’s like building a personal Google Universal Search page but you have complete control over sources that are displayed in the search results. And since WebMynd would search the other sources after displaying the main Google results, you won’t see any real dip in performance or speed.
The results are neatly embedded in the right side of the Google page and you can easily re-order and / or hide any of these services. WebMynd will remember the settings even if you exit the Google search page.
WebMynd also includes a recording feature (disabled by default) that keeps a track of all websites that you may have visited inside Firefox. If you are worried about privacy, keep this feature "OFF" as this data is periodically uploaded to WebMynd’s servers for history search visual playback.
Best of all, the new release works with Yahoo and Windows Live Search as well.
I think most Google users will love the WebMynd Firefox extension but Google may have issues with it since it pushes the AdSense ads way down the search page that they are almost invisible.
Related: Make Google More Useful