I love to design new interactive activities with existing programs. I have used Word, Excel and PowerPoint to build some pretty unconventional activities that most people wouldn't think they could do with them. If you don't own Microsoft Office and want a free alternative, check out OpenOffice Suite. You can do basically the same things and the MS Office documents will open in OpenOffice Suite.
If you use Audacity to record the commands and speech elements for a communication board, you can save them as a wav file and literally embed them into images as action settings on a PowerPoint slide. You can link images to open other slides so you can have branching communication topics just like in Boardmaker and Speaking Dynamically pro. The only difference is the switch activation. You can't set PowerPoint to scan through images but you could use the software Click it! by Intellitools to set up hotspots that would scan through the hot spots on a PowerPoint slide if you wanted to do that.
I have posted a new video on Youtube that walks through the steps to make a slide in Powerpoint that has embedded sound just so you can see how to do it. It has the Audacity step too.
All the best to you!