Google has a fabulous new(-ish) tool called Correlate
where you can draw lines on an empty graph and Google will try to find search trends that match. You can find some really interesting curves by dicking around this way. For example, searches for "how to write a resume for a job"
go through the roof from 2008 to today. Also, it turns out that people tend to google "work out equipment"
around the holiday season. [more inside]