pptPlex is a concept tool developed by Microsoft Research Labs that allows you to zoom in and out of slides much like what is possible to do in Prezi.
pptPlex has been discontinued and last updated over a year ago, but if you are interested, it is still available for download.
pptPlex uses Plex technology to give you the power to zoom in and out of slide sections and move directly between slides that are not sequential in your presentation.
On this page: http://www.officelabs.com/projects/pptPlex/Pages/default.aspx you can watch a few videos to see how pptPlex can help you organize and present information in a non-linear fashion.
Download link: http://www.officelabs.com/_layouts/olsite/TryIt.ashx?downloadUrl=http://officelabs.vo.msecnd.net/4fcaa65e-086d-4d49-a292-a5e764667263/22.214.171.124/pptPlex.msi&project=pptPlex