Here's a great example of an open source productivity tool. It does everything that Dropbox does and more. I also run it on the same network that Dropbox runs on so I'm essentially cutting out the middleman. The server software is free to download and install. The desktop apps are free. The mobile apps are 99¢ which is basically free.
* Cheaper per person than Dropbox.
* More options than Dropbox - calendars, notes, tasks, web bookmarks, contact management, integration with other cloud storage services.
* Active developer community contributing to the project.
* Your data is completely under your control
* Much more private than other options
* The software is free, but it costs me $200/year to host this free software for the people who are using it.
* You have to know how to setup and maintain a Linux server.
* There is community tech support, but you're expected to know Linux administration and bash command line tools.
* You'll need to know how to manage SSL certificates.
* Security is your problem. If you don't know how to lock down a server, you'll prolly get hacked.
* Data backups are your responsibility. You'll need to write a script to handle that for you.
* Because it's open source, there will be weird bugs that require you to patch source files on your server if you want the fix before the official release which may be weeks or months away. That'll be your call. Is the patch good? You'll have to review the code and decide.
For me, this free, open source software is a good deal because I know how to handle the things on the 'Cons' list. This open source software saves me money and only costs me a little time because I know what I'm doing.
If there's anyone else in this group with an AWS or Rackspace account, you might want to check this out.