On Google's official blog they've posted about how they randomly test new features to enhance search results (http://googleblog.blogspot.com/2006/04/this-is-test-this-is-only-test.html) and gave some examples. I think all of the examples have already been discussed on this site before (except maybe searching job listings).

"From time to time, we run live experiments on Google — tests visible to a relatively few people – to discover better ways to search. We do this because there’s no good substitute for understanding how real people, in real-world situations, actually operate. Theories are fine, but “improving the user experience” really happens best when we understand what people do online.

So to learn more, we sometimes randomly select a group of people to see a possible improvement to search options. Or we may select a group of people and try out a new element while they're searching. If you ever wonder why your Google site looks slightly different from that of the person sitting next to you, this is why."

Apparently, they've also recently added a link to a Google Reader feed (http://www.google.com/reader/view/user/10949413115399023739/label/officialgoogleblogs) of all official Google blogs, much like the page Phillip created. Is it possible to subscribe to this feed elsewhere, or is it only a Google Reader feature because it is using labels?

Hmm, the last link loads endless for me...

I got the link from http://googleblog.blogspot.com/ under the "Recent posts from more Google blogs" section.