Often when people talk about Google it is as if it is something stable. But things are always moving on. There is an interesting, if somewhat high-level, overview of search quality by Udi Manber on the Google Blog which talks some of the ways in which Google decides how to enhance its services. He talks about quality assurance, the ranking algorithm, anti-spamming measures, internationalization and new features. Things do not appear to be taken for granted ....
The most famous part of our ranking algorithm is PageRank, an algorithm developed by Larry Page and Sergey Brin, who founded Google. PageRank is still in use today, but it is now a part of a much larger system. Other parts include language models (the ability to handle phrases, synonyms, diacritics, spelling mistakes, and so on), query models (it's not just the language, it's how people use it today), time models (some queries are best answered with a 30-minutes old page, and some are better answered with a page that stood the test of time), and personalized models (not all people want the same thing). [Official Google Blog: Introduction to Google Search Quality]
I was thinking of this as I noticed a couple of Google features recently.
The first is the incorporation of local results, based on presentation of a zip code.
And here is what you get next time:
Second, I notice that Google is including a local site search in some results.