Amazingly, this free tool is still available for download (as of May 4, 2016) . I first discovered it back in 2008. I'm not sure it has been updated recently, but it's still an excellent tool for layout workflows, and other aspects of systems design. If you are still looking for a design tool, this is a good place to start.
It's a free, community edition tool to build software prototypes, design workflows and document requirements. It’s called Prototype Composer. And as of this writing, Serena is giving the tool away for free. ( after requesting, they send you an email to download the tool)
While it does have a few shortcomings, overall it is easy to learn, easy to work with, and does a very nice job of combining GUI wire-frames with a business workflow. In the end, you get a working “demonstration-only” prototype, and numerous word documents (template driven) that document the project, the GUI requirements, and the workflow process, among others.
The one major complaint I have is that the prototype can only be run from within the Prototype Composer. There is no ability to export the project as a sample web site. Hopefully, this will be part of their product enhancement in the future.