Once you have your data, you'll probably want to perform different statistical tests on that data. You might use programs like SPSS or Stata to run tests like Chi Square, t-tests, or regression analysis. Interpreting these results can be confusing, to say the least. The link below can help guide you through the basics of those tests and interpreting their outputs.
Data and Statistics are usually divided into two categories: Data sets that have not yet been analyzed (raw data), and statistical tables (charts, graphs) based on data sets. The following resources are focused on domestic data and statistics.
The following resources are focused on international data and statistics. By no means is this list complete. Mark is open to receiving your suggestions about additional data sources to include here; simply email him at email@example.com.