Lotus QuickPlace is a self-service web tool for team collaboration, providing shared team workspace. Easy management of users directly or based on NT Domain, or LDAP. It includes provision of rooms within the QuickPlace for secured areas for subsets of users. Email notifications of pages published after check out for editing is also supported.

Available free for 45 days trial period, also per user licensing cost is reasonable.

more at
http://www.quickplace.com/
http://www.lotus.com/quickplace/