Try This Search On is a free Greasemonkey script that provides useful links to search engines based on the page that you're viewing or the search that you're performing.
On some sites, such as Wikipedia, Try This Search On can figure out what the page is about and provide links to search for more information on that topic.
When searching for torrents on several bit-torrent sites (including Pirate Bay, mininova and Demonoid) Try This Search On will provide links to search a variety of torrent sites.
When viewing several movie-related web sites or television-related web sites (such as IMDb) Try This Search On will provide links to search a variety of movie and tv sites.
The bar that Try This Search On creates with the search links can be moved from it's default position at the bottom of the screen up to the top. When on top it moves off the page when you scroll down.
Try This Search On is fully customizable. You can define your own custom search engines and decide which links appear for which types of searches. You can also change where the search bar appears on the screen.