From Sheridan Libraries at Johns Hopkins University. A great place to start when looking for datasets. Clear description of sources with categoreis for demographics, economics, education, health and ICPSR. Another great tool by a librarian: Jen Darragh
Great site from the University of Chicago. Includes a comprehensive list for economic, education, health, public opinion, statistics and software. You won't be able to access everything, but it is a good place to start.