A recent supplement to KM Magazine on Collaboration had a handy classification from Tim Butler, CEO Sitecape (looks interesting as a collab suite, by the way)


Library: long life content, many consumers, few creators, littlle or no feedbck
Solicitation: more respondents than requestors. Requestors often hidden (e.g. survey), usually moderated
Team: members share objectives. Read and Create about balanced. Small membership.
Community: self-grouping, larger than a project, some members just read but all encouraged to write too. Moderation common.
Process Support: self-service, routine or complex processes with rules. Peer-to-peer often triggered by exceptions. Often combined with other models.