We use Tiki at the Phoenix site. It's AFAIK the most full-featured wiki package around (actually overkill if you just need a standalone wiki). It's great because it goes beyond the standard wiki concept of user-editable pages. You can assign permissions so that certain groups can view, edit, etc. pages on a page-by-page basis. Also roll back versions, compare versions side by side, get a list of differences, place images in pages, create structures of pages tutorial-style that have "previous" and "next" links at the top. It goes on and on.
The full package includes news publishing, forums, blogs, file/image galleries, shoutbox, the works.
But it's a heavyweight and tends to need a lot of memory for PHP script execution. The biggest problem for the Amiga platform is that it uses CSS for layout. This can be worked around to some degree, but is a downer out of the box.
For a collaborative site, it's a terrific program. See
the Tiki home page, the
Phoenix site (only news shows to public) or
my family site (just switched to Tiki -- working on content) for examples.
-- gary_c