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.
RawTherapee - RawTherapee is a free RAW converter and digital photo processing software.
PhotoFlare - Quick, simple but powerful Cross Platform image editor.
UFRaw - The Unidentified Flying Raw conversion utility
PixBuilder - Free Photo Editing Software for PC