Garden Gnome Software offers the following panoramic image converters:

Pano2VR 2.0 beta for Windows/Mac/Linux Current Version: 2.0 beta 6b, 2008-04-02

Pano2QTVR 1.6 for Windows only Current Version: 1.6.6, 2007-07-30

What is the difference between those products?

n short: Pano2QTVR is the older product, runs only on Windows and depends on Apple's QuickTime. Pano2VR has been completely rewritten, runs on Windows, Mac, Linux, and it doesn't depend on QuickTime (hence the changed name). Currently Pano2VR is in beta and doesn't contain all the features of Pano2QTVR while other parts of Pano2VR are already more advanced than in Pano2QTVR.

You can find a detailed comparison on the features page.