The following are projects I have written and designed, most of which are based on Cocoa for MacOSX. I have also written AppleScripts and used other languages like Python, PHP, Perl, C, and Java.
Our IT department has a large wall mounted monitor that we use to keep tabs on various systems. Kiosk is a screen saver that uses plugins to generate views which are then displayed randomly or in round robin fashion. It uses some nice cross fade effects and lets you define how long each view is shown. Views are dynamically generated so they can be continuously updated with fresh information throughout the day.
We have plugins that show network status, the status or backup, and our department's calendar. It is a good way to alert people of a problem as anyone passing by may see an issue and can bring it to the right person's attention. It is also very stable and has run for well over a year without any intervention.