5 Ways to Add a Search Sidebar to Google SERPs by Ann Smarty, Search Engine Journal (Oct 12)
Ann Smarty describes five browser add-ons (two for Firefox) that add to a Google search results page another panel of search results from other sources.
The Greasemonkey script for the Google Search Sidebar strikes me as the most useful, since it does what Google should do with its "web" search.
"The script “puts aside “extra things” and get simple and neat Google search”.
Those “extras” include blended search results: Google blog search results. Google image search results, Google video search results, as well as related searches."