Darktable - darktable is an open source photography workflow application and raw developer.
PixBuilder - Free Photo Editing Software for PC
Adobe Lightroom - Adobe Lightroom is a family of image organization and image manipulation software.
PhotoDemon - Lightweight portable BSD licensed photo editor for Windows focused on performance and usability.
Dark Room - A quick, powerful photo editor that gives you control
Fotografix - In addition to being totally portable, Fotografix has a ridiculously small footprint.