Check out Opposing Viewpoints in Context (you'll need to log on if off campus) Click BROWSE ISSUES to see a complete list of topics; otherwise, just browse the site
Credo Reference Academic Core is a good place for finding many definitions of a topic. Think of it as an alternative to Wikipedia. The books in Credo are published by known authors and editors, but that doesn't necessarily make them better sources of information about a topic. (Wikipedia has been found to be very accurate most of the time. The more controversial the topic, the more skeptical you should be of the Wikipedia entry.)
YIn CREDO, you can browse popular research topics or type in a topic you are interested in.