The "viewpoints" in Opposing Viewpoints in Context are useful in that they present arguments that are generally well-researched or well-structured. These essays can give you ideas and you may find quotable passages in them. They also contain references to books and articles that you may be able to find in our databases or via Google. Note that they are generally not good evidence in the way that scholarly or statistical sources are, since they are slanted toward a particular goal.
These organizations produce research on a large number of issues, most of which they make freely available online. They are biased; they are trying to influence policy. So you should be aware of their orientation and take it into account when you quote their reports. Use the site's search box, or browse the section called "reports," "research" or something similar.