If the developers still need to maintain 'real' documentation (s.a. Word documents), I see no way to meaningfully duplicate that on a Wiki.
- It does not make sense for people to write twice
- Any duplicated data is prone to get out of sync, soon.
What my current customer has done is move all this to Wiki. So I only document once, and I do it on the Wiki.
This is okay. Working with Wiki is more tedious than with Word, but at least the doc is online and others can mix-and-match with it.
Another working solution (imho) would be to store docs alongside the source, on subversion. But then the merging system needs to be able to cope with rich text etc. as well. I don't know, if any solution for that exists (other than using HTML or LaTex, which actually would not be bad picks).
