Bill Drew, Web4Lib Cool Guy, has created a Google Custom Search Engine (CSE) that searches over 225 sites. The sites are drawn from the 1999-2006 annual lists issued by the Machine-Assisted Reference Section of the Reference and User Services Association of the ALA. You can try out the engine at http://www.google.com/coop/cse?cx=012681041057676717069%3Alxoys7hon_y .
A search for Mae Jemison found a variety of sites on the first page of results, including CNN, Factmonster, Infoplease, Biography.com, and the Internet Movie Database. There was a not a full count on the search results page — is that missing from coop search engines?
By the way, LOTS of folks out there making custom search engines. Wanna find them on Google? The magic search modifier is inurl:cse inurl:coop site:google.com . Add that to a general keyword search and your results will be Google custom search engines. (Actually you might get a couple of listings that are results pages for custom search engines. If you get too many of those you can filter them out by adding intitle:custom to your query.)
A vanilla search for inurl:cse site:google.com inurl:coop gets something over 3300 results.
I did a few general searches just to see what I’d get. A search for solar inurl:cse inurl:coop site:google.com got three results, including one search results page. A search for politics inurl:cse inurl:coop site:google.com found 17 results (yow!) And a search for library finds 84 results (not much of a surprise there.)
For extra credit: if you search for a site instead of a keyword (like cnn.com instead of solar) you’ll get listings of engines which note that that particular site is being searched with their custom search engine.