Google Correlate
There's certainly the potential to extract interesting data here, but I haven't found it yet.<p>I do note with distress, however, that:<p><a href="http://correlate.googlelabs.com/search?e=why+is+my+poop+green&t=weekly#" rel="nofollow">http://correlate.googlelabs.com/search?e=why+is+my+poop+gree...</a><p>searches for "Why is my poop green?" peaked in March 2010 before subsiding, and that it's correlated with "hiv symptoms in women" and "how to get a guy to ask you out".<p>Meanwhile, "why is my poop black?" is correlated with "How to say I love you in French"