Diane, Chris, and everyone,
Scaffolding is a confusing and broad term. My understanding of it is that it is the difference between what an individual can learn on their own vs. what they can learn with an expert, guide, teacher, and/or, in the case of CoPs and situated learning, peers.
After that it can take any form (e.g., a list of procedures, graphic, CD-ROM, Web site, etc.). CoP theory embraces social scaffolding via collaboration among peers and facilitators, which is one type of scaffolding.
Prominent researchers in computer-based and social scaffolding are David Hannifin, Susan Land, and Kevin Oliver.