Debatabase- you can browser topics alphabetically
Debate Central- "Debate Central is an online resource created and maintained by the National Center for Policy Analysis for high school students researching the nationwide high school debate topic."
Fact Check-project of the Annenberg Public Policy Center of the University of Pennsylvania; " a nonpartisan, nonprofit “consumer advocate” for voters that aims to reduce the level of deception and confusion in U.S. politics. We monitor the factual accuracy of what is said by major U.S. political players in the form of TV ads, debates, speeches, interviews and news releases."
Google Scholar- searches only scholarly or academic articles
Middle School Topic Research Guide- nice listing of debate topics and sites related to that topic
New York Times Opinion Pages- varied topics
Points of View- database included in an EBSCO subscription
Pro-Con.org- covers 49 controversial issues
Times Topics- topic page collect news, reference and archival information, photos, audio and video files; goes back to 1981