In the 2008 offering of Math 154, Professor Paul Bamberg had small weekly sections where students prepared problems from the textbook in advance, which they presented for each other.
In Math 152, Professor Paul Bamberg and his co-teacher structured the class in a seminar format, where students did mini-lectures for each other in class and critiqued each other content as well as style.
Every aspect of Math 121 is highly interactive: Students spend most of classtime working in groups on problems and they then present their work and discuss as a class. Each student is responsible for some part of the in-class problems.