Brad Hinton mentioned his 2003 IAMA Conference paper, Knowledge Management and Communities of Practice: an experience from Rabobank Australia and New Zealand (pdf). It's another useful case study of KM and Communities of Practice.
ABSTRACT: Knowledge and information transfer have become important ingredients for an organisation’s competitive advantage. Knowledge management has emerged as an overarching strategy to enhance knowledge creation, information transfer, utilisation, and reticulation in order to generate innovation and improve organisational performance. Part of this strategy involves the creation of Communities of Practice. These are networks of individuals with a common, shared purpose grouped together to facilitate knowledge building, idea creation and information exchange. The experience establishing Communities of Practice at Rabobank Australia and New Zealand is examined.
The paper provides several pages worth of background on knowledge management and communities of practice, as well as references into the deeper literature if you need to read more. If you don't have a favorite resource, this could be useful for that purpose.
The specific case of communities of practice is interesting in that it was a fairly "low tech" implementation. They used e-mail as the primary communication mechanism, which has the advantage of familiarity and the disadvantage of the lack of centralized management of the conversations. From the report, it sounds like this worked very well for the initial stages of the project.
To kick-start the communities, Hinton called them "pubs" that revolved around relevant topics for the bank. Pubs are exactly the kind of place where people gather to talk about what's happening, and it was a great metaphor to use for the virtual meeting places. In combination with the mostly-informal tone of email, this makes sense.
I like the discussion here because it is not necessary to use more sophisticated means to establish effective communities. They already exist in the cafeteria, at the cafe, around the water cooler and in informal e-mail groups. This case study suggests that adding a little structure to those e-mail groups might be enough to advance the needs of the communities.