Today must be the day for lists. NiemanJournalismLab published a list of the top 15 newspaper websites according to traffic. It's interesting to compare this to Editor and Publisher's ranking of all news sites that they published last month. Apparently Huffington Post is pulling in about 7 million readers, about on par with the fourth ranking website on Nieman's list, the LA Times. This just goes to show that you should compare HuffPo to other news gathering sites rather than to other blogs.
It's also interesting to look at their highest month of traffic. Many times they will list what caused it: for the NYTimes it was the Elliot Spitzer scandal, for the Wall Street Journal it was the Lehman Bros. collapse, for the Boston Globe it was the Red Sox, and for the Politico their highest traffic was in October 2008 -- right before the election. These things all intuitively make sense. If there is news happening somewhere, you turn to the paper that has the highest profile in that area or subject matter that they specialize in. The hint then is not to do more national stories, it is to do stories that cover the subject they are supposed to cover well.