PTC is back on Mac, and today the company makes it debut on iTunes.
For the Mac, PTC has the free Creo Sketch 2.0. I'd give you the download link, but its Web page is still v1.0 for Windows only, as I write this.
For iOS devices, PTC has the free WindChill Mobile app for viewing 3D models and associated data. If you don't use WindChill at your business, the download from the Apple iTunes store includes a small data set: http://itunes.apple.com/us/app/windchill-mobile/id501201401