I’ve just stumbled across a plugin for PowerPoint called PowerMockup that contains various pre-made design elements (such as browser windows, breadcrumbs) to make it easier to create wireframes in PowerPoint.
I had a quick play with it and it seems pretty good! If you like to do your prototyping in PowerPoint, this is definitely worth having a look at.
Personally, PowerPoint is rarely my first choice when it comes to prototyping tools, mainly because there are better, more effective, purpose-built applications out there. But Powerpoint has one big advantage to many of these tools. Other people can open/edit/play around with the wireframes without having a particular software installed. And wireframes should never be one person’s baby.
I will definitely have PowerMockup in mind next time I create wireframes in PowerPoint.