There's no real offline Photosynth viewer at the moment, but you can use Henri Astre's Photosynth toolkit to download the photos, point cloud, + camera positions for any synth. http://bit.ly/photosynth-toolkit
If you're asking about your panoramas instead of photosynths, then there's no way to download a panorama from Photosynth.net at the moment, but that's possible as well if you can find a programmer to modify Henri's synth downloader. They would also need to write the software to re-project the cube map format of the panorama into a flattened format if you wanted to view them as a normal photo.
However, every source of panoramas uploaded to Photosynth.net including:
Microsoft ICE: http://bit.ly/microsoftice
Adobe Photoshop: http://bit.ly/pstops
Mobile apps: http://bit.ly/photosynthforwinphone + http://bit.ly/photosynthforios
Theta 360: http://bit.ly/psbtheta360
all generate a flattened panorama that you can save on disc or SkyDrive.