This is yet another baby out of Google Labs; Google Trends. It allows two options Words Search trends and Websute trends.
With Google Trends for Websites, you can get insights into the traffic and geographic visitation patterns of your favorite websites. You can compare data for up to five websites and view related sites and top searches for each one. Hence simillar and alternative to Alexa traffic search for websites.
While with Google trends for search word, one can find out the search history and pattern for particular word. Enter up to five topics and see how often they’ve been searched on Google over time. Google Trends also shows how frequently your topics have appeared in Google News stories, and in which geographic regions people have searched for them most.
Its still in release version and hence available only in English.