I am probably very, VERY behind the times on this, but I recently discovered Google Trends.  Its a site where you can type in search queries, and it will graph you out the number of times that search has been done using Google since they started keeping that information (seems like 2004).  Seeing the trends in single searches is pretty neat, but the fact that you can do multiple searches at once, by separating them with a comma, makes it neat to see correlation.  Here’s a couple I did recently that I thought were neat.

Wii(blue), PS3(red), XBox 360(orange):
Wii Three Three-Six

It’s interesting to see the trends in searches for the 3 current-gen consoles  because it shows their popularity compared to each other as well as the fact that they spike, as I am sure all things kids want for Christmas do, right around the winter season.  Doing a similar search for DS and PSP actually returned similar results, only the PSP was nearly twice as popular as the DS, which is not what I would’ve thought.
Cough(blue), Bronchitis(red):
Cough, Bronchitis

This is neat because it shows just how seasonally regular the common cold really is.  Taking this idea and seeing any trends with the flu didn’t not turn up the same sort of periodic results.  Instead, it just had a few very high peaks surrounded by drastic falloff.  I am guessing this goes more with the “epidemic” nature of the flu.

And my personal favorite:
What time is it:

Do you see the pattern there?  Those spikes occur twice a year, right around the daylight savings time time changes.  There are some peaks happening in the summer as well, no idea what those are caused by.
At any rate, I think it is a neat time killer to try and see correlations in searches.