The Google trends for websites, which was released by Google 3 days ago, is really something to check out if you're interested in comparing website metrics between different websites and across geographical locations.
Alexa and Compete offer similar services. One of the features that stands out with Google trends is that it displays related websites that visitors to the website being viewed visit in descending order of visitors. This related websites are also filtered when filtering down to single geographic locations. This makes Google trends for websites quite a bit more powerful for your research. It allows you to view a websites competitors in each geographic location or allows link building and search engine optimization for a website for each geographic location.