Recently npm added back download stats, which means you can see how many downloads a package has had. The announcement includes the note that Mikito Takada submitted a pull request for the D3 graphs -- it's things like this that make me glad npm's website is open source.
There's a public API for the statistics, which is written using hapi.
Paul Vorbach sent in npm-stat (GitHub: pvorb / npm-stat.com, License: MIT), which generates another set of views on npm's stats. It displays downloads per day, week, month, and year, and there are graphs for authors as well. Pages for certain authors that I won't link to directly naturally take a while to generate, but it's generally fairly responsive.
I'm interested in seeing what people build with npm-www and the stats public API, but so far it seems like they've made a big improvement over the older versions.