JPEGDeux is a program that displays slideshows of image files. The shows can be displayed in a window, full screen, or in the Dock (!), and there are several customization options.
The name comes from the program JPEGView, which I admire as a specialized tool that works intuitively and is done right (it still runs great in the Classic environment despite being written in 1995). JPEGDeux is open-sourced under the BSD license. The code demonstrates some interesting Cocoa techniques, such as short-circuiting the main run loop and a customized image view.
Version 1.8: Compiled code with XCode 2.1 - Fixed but that would cause JPEGDeux to crash on startup (deleting the plist file was the previous solution to this issue). - Fixed "niggly" little issues with the GUI.
Mac OS X 10.1 or later