If you're up for a really large visualisation challenge, the Statistical Computing and Graphics Sections of the American Statistical Association has just announced its 2009 data expo challenge - http://stat-computing.org/dataexpo/2009/
This year the challenge is to analyse and summarise airline on-time performance data. The data is very large: 120,000,000 flights spanning the last 20 years, but the website does provide a few hints to get started, and you're welcome to work on a smaller subset. However, the payoff is large too - hopefully you'll be able to predict (or at least better understand) flight delays and cancellations.
Traditionally, this competition has only been taken up by the statistical community, but we're keen to get a wider involvement and will be working to ensure that the barriers to participation are as low as possible.
