Local, regional and national newspapers and other news publications are great places to find opposing viewpoints on a variety of topics. For example, The New York Times and The Wall Street Journal have opinion sections with viewpoints on political, social and environmental issues.
Editorials or opinion pieces are usually written to be persuasive, to motivate the reader to agree with the writer's point of view. These articles are usually clearly labeled as opinion.
Be sure to scrutinize opinion writing by looking for factual information or sources the writers use to support their opinions. Use the CRAAP Test to determine if the information presented is reliable.
Think tanks, policy institutes, and research institutes perform research on specific topics. It's important to know how the organization is funded, the credentials of its researchers, and if it advocates a certain point of view or political or social agenda.