Last year, one of my colleagues organized learning tours at our school -- a more group oriented version of learning walks. To make it a little more fun, we mocked up concert tour posters for the teachers who were being observed based on the teacher's favorite musician or band.
As revealed in the debriefing process, our colleagues walked away from these tours inspired and with new appreciation for the work of their peers and what they might do differently.
Some teachers also shadowed students for a day -- specifically 10 of our middle school teachers as well as the middle school principal.
This is similar to the contribution that Jessica Lura posted here.