I chose "the death penalty" as their topic of debate because that was the subject of the last debate I was in back in high school. My own opinion is that most problems with the death penalty are actually the fault of the appeals process - if you simply tightened the criteria for placing someone on the death penalty, you wouldn't need such a bulky appeals process. As it stands, the appeals process is what makes the death penalty economically whack, since it's used both by people who should have never been put on death row in the first place, and by people who do deserve the death penalty but are using the legal system to prolong the inevitable for waaaaaaaay too long.
Anyways, this is the series idea I came up with. Let me know what you think.