"Correlation is NOT the same as causation".
I don't know how many times I've said it (haven't we all?) in class, to the T.V. announcer, ...........
Tyler Vigen is a grad. student at Harvard Law School. He has a fun site called Spurious Correlations. Here are a couple of examples:
As of today, there are more than 23,000 spurious correlation charts on Tyler's site. You can even sign up to get an RSS feed of a new spurious correlation every day, if you're so inclined (or even if you're standing up)!
(r = 0.9357)
(r = 0.9805)
Yes, the sample sizes are small; and yes, I'd like to see more economic examples. However, I can still see myself using this material in class!