Darktable is a virtual lighttable and darkroom for photographers: it manages your digital negatives in a database and lets you view them through a zoomable light table. It also enables you to develop raw images and enhance them.
Panopano is a 360° Panorama viewer (Java/Java3D), and can also be used as a view editor (extracting/importing a "normal" view). It can display equirectangular and cubic panoramas, and virtual tours (popup images/video transitions between panoramas