Windows with Office 2007 only: pptPlex, a free Office add-on, makes PowerPoint presentations less of a one-way street and more of a neighbourhood exploration. After installing the add-on, you’ll be able to put slides together in groups, slide around the canvas during a presentation, easily zoom in on charts or stats you want to highlight, and generally make the presentation more open to give-and-take and audience questions. Check out the video above for an overview. pptPlex is a free download for Windows systems with Microsoft Office 2007.