DebatePedia is a wiki meant to support and provide a forum for actual, reasoned debate on current events topics. I've poked around a bit, and it looks like a fascinating space to play.
For instance, the Same-Sex Marriage section seems like a solid start to the published opinions presented on the topic, as addresssed through a series of subquestions.
This would be perfect for an older high school student -- I'd show them this and the Opposing Viewpoints database we have accessible through our website, then ask them to compare and contrast the material provided through both of these sources and see if they consider the results to be well-rounded.
I also pointed this out to my husband, an inveterate debater. No answer from him yet on the coolness factor.
(I found this via one of the blogs on my soon-to-be-added blogroll over there. Check 'em out!)