A good reference document on OCHA's CMCS from December 2006, that describes the structure, function and role/responsibilities in the humanitarian community.
Interesting to look back upon the role given CMCS (then CMCoord) in 1995:
"The Unit aims to facilitate timely, sufficient and cost effective support by military and civil defence assets to concerned humanitarian agencies when requested. It will act as a focal point for governments, regional organizations, military and civil defence institutions interested in planning and, when requested, providing support to agencies engaged in humanitarian operations. The Unit will support the establishment of preparedness and response measures, the development of planning tools (databases, manuals), the definition of a legal framework for the use of military and civil defence assets, and the preparation and implementation of training exercises."