Have students become the teachers as they collaborate to design a lesson that presents the content to their peers. For example, this rubric (and PBL idea) was originally used during a PBL that supplemented my unit on Meso-American Empires. Each group was assigned a content standard and an empire to research further. Then, as they worked through the PBL process, they designed a lesson that could be used to present and get their "students" to interact with the content.
This rubric could be applied to all content areas as long as you follow this simple formula: provide students with a content standard and/or topic; give them time to collaborate, plan, research, and create; and sit back as they teach the class.