ICPSR is a great place to find data sets for your research, learning, and teaching. It maintains a data archive of more than 500,000 files of research in the social sciences. It also provides teaching tools such as exercises and resources for students & teachers.
To search for data in ICPSR, simply type a topic into the search box (broad topics work best). You can also browse by topic.
After you have your results, you can limit by data format, restriction type, and more.
PRO TIP: If you are searching for data sets for use for a class assignment, select "Public Use" for your restriction type. This will enable you to access the files that you need in specific formats (for example, SPSS).