General Reference: Free Data Sets

Dryad

• Data included: Multidisciplinary. Works with a wide variety journals to include data sets associated with published articles.
• Frequency of data collection: New data is constantly added.
• Use of the data/Permissions: "The data hosted by Dryad have been dedicated to the public domain, to the extent possible under the law, under the terms of Creative Commons Zero (CC0), in order to minimize legal barriers and maximize the impact on research and education." More info on their FAQ.

The European Social Survey

• Data included: Covers over 30 nations. The questionnaires is approximately 240 questions and covers a wide range of social variables.
• Frequency of data collection: Every other year.
• Use of the data/Permissions: "The data are available free of charge and without restrictions, for not-for-profit purposes. To access data files, you have to register as an ESS data user."

World Values Survey

• Data included: The 2011-12 survey will cover at least 50 countries. The data collected is for the purpose of "studying changing values and their impact on social and political life."
• Frequency of data collection: Approximately every 5 years.
• Use of the data/Permissions: "These data files are available without restrictions, provided: a) that they are used for non-profit purposes; and b) correct citations are provided and sent to the World Values Survey Associations for each publication of results based in part or entirely on these data files. This citation will be made freely available; and c) the data files themselves are not redistributed."

• Data included: Multidisciplinary. Health, environment, public safety, and much more!
• Frequency of data collection: New data is added all the time. Some data sets include information from the current day!
• Use of the data/Permissions: Free to use. You will be asked to agree to Terms of Use before accessing the information.