There are many research organizations which make available datasets via the web. At this point there is no perfect search mechanism for sifting through the content of all these collections. The links below will take you to web portals which seem to be the best available. Note that these portals point to both free and pay sources for data, and to both raw data and processed statistics. Pay sources are marked with an asterisk.
Selected datasets on the Internet, arranged by topic
The organizations listed below are included because they offer free download of significant datasets. There are a few organizations in this list that offer certain datasets at a cost. Those listings are marked with asterisks (*). Some of the organizations below have deposited their data with ICPSR in addition to offering downloads from their own website.