Inquisitor calls itself Spotlight for the web. The free search plugin is installed in Safari and provides better search results using Safari's built in search box. When a user enters text into the input, Inquisitor displays a drop down menu with results suggestions and search term auto-completion. The first section of the drop down shows matching results pages in Google, and in the second section shows auto-completion suggestions for other terms that match the entered text. If you edit the search preferences, you may also see links to narrow your search to a particular search engine, e.g. IMDB, Flickr, Google Blogs, etc. You may also set keyboard shortcuts to quickly trigger results from one of the search engines you've added.
