Recently when trying to better understand patterns of searches at Michigan State University I color-coded related search terms and analyzed 13 months of data. Not too surprisingly more people seek football tickets in the fall, bookstores at the beginning of the school year, and information on academic probation after grades are posted.
This is a pretty basic approach, one that wouldn't work well for folks with color blindness. I'd love to have a tool that learns related terms and clusters them for you.
Lou Rosenfeld and I are working on a book explaining the value of search analytics; you can find more information about seasonal clustering and a link to my color-coded spreadsheet.