Hi all,
I have tried out Google Docs, and it is possible to keep there and work collaboratively on documents that were originally written in MS Word format.
For instance, this is the DimensioneX Readme:
http://docs.google.com/Doc?id=ddgw8hz2_2cqhjd3hhIt is not a WIKI, but however I can enable anyone having a @gmail.com account to work on it.
For the Developer's Reference, it seems not straightforward - The upload feature accepted a version trimmed up to 500 Kb and the current file is 1.8 MB. Probably content can be added in steps.
If someone is interested in helping me in it and/or working on a shared document, just let me know, and we arrange it.