We're creating a collection of useful tools and data sources, and would love to hear from you what you find helpful.  These might include:

* Commonly used datasets for question creation or answering.

* Helpful online tools for statistics, probabilities, regressions, etc.

* Resources for good prediction techniques, debiasing, etc.

And so on.  (If you make your suggestions in individual comments we can smiley-vote them as well.)