How can I work in other applications while using PowerPoint presenter view on mac?
I am assuming multiple display setup in extended mode (not mirrored).  I had this problem as well.  

I found that in PowerPoint Mac 2011:


go to "Slide Show" tab in the ribbon.  
Click "Set Up Show" button.  
Change radio button for "Show type" to "Browsed by an individual (window)".


This will put the presentation into a window, which you can maximize on the presenting screen (for me the 2nd display hooked up).  Yes you get the title bar, but otherwise it's effectively full screen.  On the primary display (which is still my laptop screen), I can move to different applications without affecting the windowed presentation screen.