Search Radar, a recently launched browser plugin, aims to help users refine their search results by providing suggested queries based on their search terms. When the plugin is installed, the Search Radar suggestions are delivered in the sidebar of the search results page.
Search Radar works by analyzing the search results for your query and figuring out which terms appear the most across all results. The idea is that while searchers tend not to search beyond the first page of results, Search Radar's suggestions, because they're drawn from all results, will point you toward related topics you may not have found otherwise. Search Radar also says they're results provide an overview of the topic you're searching for, without having to dig through the actual results.
In Google, the suggestions replace Google's search ads completely (in Yahoo! they just move the ads down the page a bit). The suggestions are the same for both sites, however (and match the suggestions given when searching via the Search Radar site). That, and text on the web site, indicates that Search Radar isn't basing its suggestions off of the results from the search engine you're using, but off of its own crawl. That also explains why some, more obscure searches, turn up no results -- their crawl just doesn't cover that particular part of the web.
Search Radar suggestions (highlighted) appear where Google's text ads would be.
I wanted to compare Search Radar to the new Yahoo! Search Assist program (which we wrote about earlier this month), because it works in a similar manner. Yahoo!'s search suggestions are based off the top 20 pages for your search results, rather than the entire query results that Search Radar uses. Because search engines attempt to deliver the most relevant results first, suggestion based on only the top few might better cut down the noise from the signal than suggestions based on the entire results of the search. Unfortunately, it looks like I'm no longer in the test group for Yahoo! Search Assist, so I was unable to run any comparisons.
As for Search Radar's suggestions, they were actually not bad for most searches. A search for hockey great 'Wayne Gretzky,' for example, suggested that I search for the Edmonton Oilers and New York Rangers (two of the four teams he played for), the Phoenix Coyotes (the team he now coaches and owns), Mario Lemieux (his chief rival during his career), Mark Messier (his long time teammate), and Sidney Crosby (considered by many to be his heir apparent).
Thanks to Singh for the email tip, and hat tip to StartupSquad as well.