One of the most interesting things about sites that aggregate data is what they can say about trends over time.  The more popular the site, the more interesting its trend data.  Wikirank is a site that tracks activity on Wikipedia pages over time.  Graphing the results to show changes in page popularity.  Out of the ordinary spikes generally reflect a news worthy event.  The site also allows for a number of pages to be compared for more long term data.  The image above shows the popularity of each of the Beatles' members.  Clearly John is the most interesting (to Wikipedia readers).