Scrum is a light-weight, collaboration-based project management methodology that has a lot in common with
OpenSpace. It was designed for Software Development, but has been successfully used to tackle various other kinds of "Wicked Problems" from planning a wedding to running a museum.
The ScrumMaster is the person taking the leader/facilitator role when using the Scrum methodology. It also designates someone who has completed Certified ScrumMaster training.
http://www.c2.com/cgi/wiki?ScrumMaster
related pages: GrowingAgilePractices2004, sponsored by ScrumToronto