I've used Google Trends to do a few trend charts of various technologies, but this article, "Unexpected Decline in Existing Home Sales? Not Exactly" shows a wonderful example of online search usage as a precursor to real-world activity (in this case, searching on "homes for sale" before buying a house.) The chart below summarizes it [Ed. the chart no longer exists--nor does the article], but you might want to click through at take a look at the full post (it's short but interesting.)