Professor Ned Hall's students learn logic in an interactive, engaging way. Problem sets are done on deductivelogic.org, where students can immediately see how they are doing. If they are having trouble, they can post questions and respond to each other's questions. These assignments are not graded, but the problem sets relate directly to the weekly quizzes, which do count, and include at least one questions from the problem sets.
Deductivelogic.org also allows users to design their own courses, where they can post syllabi, lectures, grades, and announcements. Students or instructors can try their hand at designing their own logic problems and get instant feedback on them. Check it out here.