I second Luke's answer.
I can Recommend Confluence and here is why:
I tested extensively many commercial and free Wiki based solutions. Not a single one is a winner on all accounts, including confluence. Let me try to make your quest a little shorter by summarizing what I have learned to be a pain and what is important:
- WYSIWYG is a most have feature for the Enterprise. A wiki without it, skip it
- Saying that, in reality, WYSIWYG doesn't work perfectly. It is more of a feature you must have to get the casual users not be afraid of the monster, and start using it. But you and anyone that wants to seriously create content, will very quickly get used to the wiki markup. it is faster and more reliable.
- You need good permissions controls (who can see, edit etc' a page). confluence has good, but I have my complaints (to complicated to be put here)
- You will want a good export feature. Most will give you a single page "PDF" export, but you need much more. For example, lets say you have an FAQ, you want to export the entire FAQ right? will that work?
- Macros: you want a community creating macros. You asked for example about the ability to rate pages, here is a link to a Macro for Confluence that lets you do that
- Structure: you want to be able to say that a page is a child of a different page, and be able to browse the data. The wikipedia model, of orphaned pages with no sturcture will not work in the Enterprise. (think FAQ, you want to have a hierarchy no?)
- Ability to easily attache picture to be embedded in the body of the page/article. In confluence, you need to upload the image and then can embed it, it could be a little better (CTR+V) but I guess this is easy enough for 80% of the users.
At the end of the day, remember that a Wiki will be valuable to you the more flexible it is. It needs to be a "blank" canvas, and your imagination is then used to "build" the application. In Confluence, I found 3 different "best practices" on how to create a FAQ. That means I can implement MANY things.
Some examples (I use my Wiki for)
- FAQ: any error, problem is logged. Used by PS and ENG. reduced internal support time dramatically
- Track account status: I implemetned sophisticated "dashboard" that you can see at a glance which customer is at what state, the software version they have, who in the company 'owns" the custoemr etc'
- Product: all documentation, installation instructions, the "what's new" etc
- Technical documentation, DB structure and what the tables mean
- HR: contact list, Document repository
My runner up (15 month ago) was free Deki_Wiki, time has passed, so I don't know if this would be still my runner up.
good luck!