Developer website: Pangea Software
PanoPreviewer is a Photoshop plug-in for Mac OS X that allows you to almost instantly preview equirectangular images as VR panoramas. Normally when editing an equirectangular image you're constantly saving the file out and loading it into a utility like CubicConverter so that you can preview it and see what needs touching up. With PanoPreviewer the tedium of that process has been eliminated since you can now preview the pano right in Photoshop!
Mac OS X 10.4 or later, Photoshop.