Bluespice MediaWiki is the enterprise circulation of the illustrious Wikipedia Tool MediaWiki. Apart from its useful features such as discussion boards, content management, categorization etc, I love their pricing structure. You can request a 30-day free trial from them and that has every feature you want right from SSL protection, no user limitation and best of all a couple of hours of support too. They are so confident in their product that they are happily offering the "try before you buy" and you can extend your usage after your trial at a cost.

Plenty of great features with Blue Spice Mediawiki, such as an open-source basis, and if you like to try it out for free, you can do so as a virtual machine image for VMware etc and then once satisfied, the business version is a paid one with 83 Euros a month starting price.