update 5/6
rw: More on GgW 'type' keyword (GgOS w/links)
Google Semantic Web (Google Reads Your Mind) ~new~revolution:

After seeing that Google has word categories

-- 5/5 post: It would be nice to find out that Google has created a hierarchy of words and expressions similar to Wordnet's synsets and indexes web pages not just for words, but for their meaning. So maybe in the future, we could search for [apple type:fruit] and get only results about fruits, not about Apple Computers. --

a new feature shows Google working on a new approach to search: a semantic web without a special markup language. the new feature is it a feature if you can't turn it off? (& go back to the old way) allows users to refine the search by choosing its direction.

eg search for [tired] can choose: > medical treatments > alternative medicine suggestions >research papers > news. these refining options appear at top, below are unrefined search results (right?) so ok not a loss of the old happy mishmash.

You can view the live Google search here
= http://nico.nfshost.com/wp-content/uploads/2006/05/search.htm ?
~ same as http://www.google.com/search?sourceid=navclient-ff&ie=UTF-8&rls=GGGL,GGGL:2005-09,GGGL:en&q=tired ?
and more comments at Nico's Blog, where says this is search-results-clustering.
I think it's not just clustering, it's understanding user's intentions and providing a better experience. hmm - "not just" ie because clusters are useful ones? or what more to it?