Pro/Con Lists lets you identify a topic, lists arguments for and against it, lets you add a “rational weight” and “emotional weight” to each argument/reason, and then provides you with a pie-chart reflecting all the calculations.

It’s easy to register and to use and might be a useful writing/thinking exercise for students. It’s possible that the site might have some accessible lists that might not be appropriate for the classroom, but I didn’t see any at a quick glance.