If you don't have any idea what you want to write about, here are some sources that you can scan for ideas that appeal to you:
The Encyclopedia of Contemporary American Social Issues. Full text reference source, online in the eBooks Academic Collection from EBSCO.
The CQ Researcher in the Congressional Quarterly Electronic Library. Weekly summary of a topic in the news, not all of which are social problems. To see list of topics:
Scan the list for topics of interest to you.
The database TOPICSearch. Scan the Current Events and Topics in the search options for areas of interest. Highlight, then click Search.
Go to the list of subject guides, which is also on the homepage under Find > bySubject
Look for the one which is closest to the area you are considering.
Search the core resource with a general keyword similar to current events, controversy, ethics, social problem*, etc.