I heard about this on FLOSS Weekly’s interview with Ben Goodger, one of the creators of Firefox. They asked him what features in Firefox are underused and he said “keyword searches.”
To use this feature, go to a site you do a lot of searching on like IMDB and right click on the search box. You’ll see “add a keyword for this search.” Add the keyword “imdb” and then hit ok. Now, all you need to do to search imdb is open a browser window and type in for the url “imdb Godzilla” and it will do a search on imdb for “Godzilla.” Pretty neat.