IT people love this app for Network maintenance notices! A simple yet powerful tool to post important alerts, notifications and portal updates for everything from breaking news, to service windows and outages, to important reminders.
Global Announcements allows site administrators to notify users of service events and outages without the hassle of emailing individual users about it.
Global Announcements provides a prominent location on every page in your site for a post. Perfect for important notices, centrally configured, with date/time to display. Can be set to show at top or bottom or page and look as you want via HTML.
http://guide.porteointranet.com/SimpleBanners/FAQs.aspx