According to the Wall Street Journal, "The company unveiled Google Trends, which allows Web users to see what people around the world are interested in by running searches of Google's Web-search traffic. For instance, a user could search the terms "boxers" and "briefs" and see on a bar chart that compares the popularity of the two terms that boxers are more popular, said Jonathan Rosenberg, Google senior vice president of product management."
The tool is simple to use, and returns some fascinating data. Enter Riesling,Chardonnay, for example, and you can see that generally Chardonnay is much more popular in say New York City and Australia, and Riesling is more popular in Germany and France.
Cabernet Sauvignon demolishes Cabernet Franc:
http://www.google.com/trends?q=cabernet ... l&date=all
Pinot Noir 100%; Merlot 0%.
And so on.