gPhoto is a program and library framework that lets users download pictures from their digital cameras. The libgphoto2 library gives you access to hundreds of models of digital cameras on several platforms. GIT repo and Issue tracker lives at https://github.com/gphoto/ these days.
ImageGlass is a lightweight, versatile image viewing application.
ImageGlass is a lightweight, versatile image viewing application that is designed to take the place of Photo Viewer in Windows 8, 7 and Vista, especially those installations that may have trouble displaying PNG and GIF files in Photo Viewer.
OpenImageManager, the new Opensource Image Manager written in C#. Includes Thumbnails feature, HTML Album Generator, localized to 10 languages and more...
Virtual Photo Organizer is a photo album, which lets you easily organize and edit your digital pictures and even lets you export them into an HTML album or burn them to a CD/DVD.