GCalert will access all your Google calendars and display alarms via libnotify for whenever you have alarms set for each event. These alarm widgets do not receive focus (and thus do not take keyboard input away from other applications), yet are clearly visible even on a cluttered desktop.
URL Notification System (UNS) uses simple Web pages to show messages and alerts around your campus. Every zone can have its own custom messages, and an emergency mode can be set that overrides all pages in all zones. Active Directory is supported for user access. RSS feeds are supported. Lists of URLs can be copied from one client to anther or from another client zone.