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.
GTK+ comic book viewer.
MComix is a user-friendly, customizable image viewer. It is specifically designed to handle comic books (both Western comics and manga) and supports a variety of container formats (including CBR, CBZ, CB7, CBT, LHA and PDF). MComix is a fork of Comix.
A full featured cross-platform image library
Developer's Image Library (DevIL) is a cross-platform image library utilizing a simple syntax to load, save, convert, manipulate, filter and display a variety of images with ease.
Comix is a user-friendly, customizable image viewer. It is specifically designed to handle comic books, but also serves as a generic viewer. It reads images in ZIP, RAR or tar archives (also gzip or bzip2 compressed) as well as plain image files.
nomacs is a fast and small image viewer
nomacs is a free image viewer for windows, linux, and mac systems, which is licensed under the GNU Public License v3. nomacs is small, fast and able to handle the most common image formats including RAW images. NOTE: nomacs has moved: http://download.nomacs.org
Project moved to Bitbucket https://bitbucket.org/andreyu/simple-viewer-gl Small and simple viewer for Linux, support multipage images, support transparency and alpha-channel in images.
Image viewer and organizer
Phototonic is a fast and functional image viewer and organizer, inspired by the traditional image viewer design (i.e. thumbnails and viewer layouts). Phototonic developed in C++/Qt and released under GNU General Public License v3.
The "Java Mass JPEG Resizer Tool" has following Features Resize all JPEG Images of a Directory, Create Webgalleries, Pack it to an ZIP File for E-Mail Attachments. The Tool is available in German and English.
Prepress image viewer and converter
Prepress image viewer and converter. Supports RGB/CMYK/GRAY/PNG/JPEG/TIFF/PSD 8/16/32 bit images and ICC/ICM v2/v4 color profiles.
AstroCam is an C based daemon process for Linux and BSD to control stepmotors via SMC 800 cards. AstroCam also includes both, an PHP-based WebInterface and one based on Perl, for remote Stepengine control. You can control webcams with it.
Geeqie is a lightweight image viewer. It was forked from GQview. The development is focused on features for photo collection maintenance: raw format, Exif/IPTC/XMP metadata and integration with programs like UFraw, ImageMagick, Gimp, gPhoto or ExifTo The current development and project can be found on http://www.geeqie.org/. The sourceforge page will be deleted soon.