showFoto - ShowFoto is the standalone image editor of the digiKam project.
RawTherapee - RawTherapee is a free RAW converter and digital photo processing software.
PixBuilder - Free Photo Editing Software for PC
Darktable - darktable is an open source photography workflow application and raw developer.
PhotoDemon - Lightweight portable BSD licensed photo editor for Windows focused on performance and usability.
digiKam - Professional Photo Management with the Power of Open Source