Atlassian's Confluence is the best of them so far. Pros: the overall design is clean, it has advanced management tools, good security, and simple attachments.Its email function has to pick mail up from a POP box which makes it a little bit less ad-hoc but still functional. And most importantly, it also has great tools for moving pages around. Cons: Text editing, like with most apps these days is a bit dodgy, and pasting in blocks of text from Word is likely to cause problems. The pricing model is reasonable but for some reason (possibly because they're from Australia), they still don't have a directly hosted option so you have to use somebody like Contegix or deploy it on your own box. This seems to be a big and obvious oversight on their part these days. Also, their pricing model doesn't encourage small deployments right off the bat. I think this is the one that we'll use more of internally at the company where I work. Summary: The best of the enterprise wikis today, and one of the best options for scalability.
