Explore the ICPSR website. Start by browsing their list of subject headings and then writing a short summary of the data sets available about one subject. You can start at www.icpsr.umich.edu/icpsrweb/ICPSR.
Try an online analysis. Go to one of the websites that offer online analysis of secondary data, like the ICPSR site. Review the list of variables available for online analysis of one data set. Now form a hypothesis involving two of these variables, request frequency distributions for both, and generate the crosstab in percentage form to display their relationship.