Let me be frank: the way we manage documents at my office is horrible. We have a central file server, but some people don't like to use it, while others tend to abuse it.  It's a real mess with long email chains of Word and Excel files being sent back and forth, and no one really knowing where or what the final version of any given document is.  Since we're a small company we don't have a lot of time to solving the problem with anything home-brewed.  To solve our document tracking/versioning problem, we're evaluating: KnowledgeTree, Alfresco, and O3Spaces.  Update: I also found LogicalDOC

Each system has a free "community edition" for download:

We're going to be installing each one into their own virtual machines, and running through trials with less technically-inclined coworkers.  (There are people who don't drool over computers? Insanity!)