Comparison and Ranking of Chinese Bookmarking, Sharing, and Recommendation Websites

With so many bookmarking sites around these days, which are the most popular ones? Clearly, veteran sites like Delicious have more users than Chinese bookmarking sites that appeared later. As for the many emerging Chinese bookmarking sites, one straightforward idea is to analyze the Alexa rankings of these sites, which can roughly estimate the traffic of major Chinese bookmarking sites.