I'm interested in actually making something with Python and learning the sciPy and/or numPy libraries. So I was thinking about data sets available to me. Another question had some people looking at the data, but very little about mathematical or statistical analysis on the data.
So, poll rules apply - one suggestion per answer. Upvote the ones you like, downvote the ones you don't. I'll begin working on it this weekend, and as I get results, I'll post them.