Many years ago on a search engine far far away…
until recently Google supported a few nifty specialized search services: google.com/microsoft /linux /bsd /mac /about and /unclesam
These services could be used to perform broad searches in specific fields and (especially in the case of /microsoft) was a much more accurate and useful search engine than the vendor provided.
Unfortunately Google abruptly discontinued these services on June 7th. For more information including screen shots of the search pages for each of the services check out this post over at blogspot.
Google claims their standard search engine has progressed enough that it will provided better results than the specialized services.
More on Google’s unofficial stance can be found here.