Chiliproject https://www.chiliproject.org/ is a fork of Redmine. I have done a test install but not used it seriously.
I've used Trac http://trac.edgewall.org/ also. I like Redmine better because it has (or had, have not checked lately) better multiple-project support.
Our "front office" folks use Alfresco http://www.alfresco.com/ but their use of it is almost exclusively as a Microsoft Word storage shed.