My partner (and wife) Rosalyn and I have needed a way to collect our work on Lunatics in a way that is easily maintained and allows for collaborative editing and for collecting all of the media and notes that we have created for the project. It may seem a little like overkill for just two people, but there are a number of advantages to installing a wiki for this purpose, and the MediaWiki software is the best I know for this purpose, since its development has been so motivated by the needs of Wikipedia.
In my opinion, choosing between proprietary and free licensing is actually choosing between short term and long term goals. If one needs something that works in a business meeting in an hour and if her/his expertise with free licensed products is slim then one is likely to choose what s/he knows "it works" and that includes proprietary software.
For someone to truly switch to "free as in freedom" software they need to set long term goals for it. Let me expand this idea a little bit.
If you are looking for a powerful yet easy to use collaboration solution, you might want to take a closer look at http://www.mindquarry.com. Groupware tools are a dime a dozen these days, but there are a few features that make Mindquarry stand out from the crowd.
I recently picked up the book Wikinomics by Don Tapscott and Anthony Williams and... bought it. This was a slightly unusual move for me as I get most of my information on what’s happening on the web from Free Software Magazine and others like it covering new developments (the web being somewhat faster to press). Being the neophyte I am, I was hoping for it to be a great compendium on current developments in collaboration.
I still haven’t found a free software case management framework for non-profits emerging on the horizon. If you search SourceForge or Freshmeat, you find legal case management systems, but nothing oriented to the general non-profit market for client management. There are electronic health records, CRMs and ERPs... all of which have elements that would be useful, but none alone can do the trick.