Jmol is a Free, Open Source molecule viewer and editor. It is a collaboratively developed visualization and measurement tool for chemical scientists. Jmol is an active project, and there are new features being added to it on a daily basis. Users are encouraged to modify it to fit their needs and to contribute their changes to the project.
QCad is a powerful but easy to use 2D CAD program for Linux, Windows, and Mac OS X. It uses DXF as its standard file format. While other CAD packages are often rather complicated to use, QCad tries to stay comfortable, and even an absolute beginner can create professional drawings with a minimum of effort.
Image Viewer is a multi-frame (animated) image viewer with real-time interactive pan and zoom viewing that uses the GTK+ toolkit and Imlib. It is capable of opening and saving to any image format supported by Imlib. It features screenshots (screen capture), crop, resizing, print, fullscreen display, display on the desktop (root window), animation (creating animated GIFs), color leveling, drawing font/text strings, and editing image header information.