I should have shown this to you before, because there is a page that provides information on the current top 25 downloaded data sets. There's also information on how much traffic the site is getting on a month-to-month basis, the total number of departments that are contributing data sets, and how many data sets from each department, and so forth.
This page is updated on a monthly basis because it continues to change. Data sets that are very popular can move up and down that scale from month to month.