Darktable - darktable is an open source photography workflow application and raw developer.
showFoto - ShowFoto is the standalone image editor of the digiKam project.
RawTherapee - RawTherapee is a free RAW converter and digital photo processing software.
PhotoDemon - Lightweight portable BSD licensed photo editor for Windows focused on performance and usability.
UFRaw - The Unidentified Flying Raw conversion utility
PhotoFlare - Quick, simple but powerful Cross Platform image editor.