Scheduled Announcements Widget is a WordPress plugin by kionae thatlets you add a scrolling list of site announcements, independent of normal posts and pages, to any widgetized area of your site, or to your theme files. Perfect for publicizing an event, alert, or notice that doesn’t require a full-page write-up. Announcements can be scheduled to run indefinitely or during a specific date range, and admins can chose between horizontal or vertical scrolling.
Download: http://wordpress.org/extend/plugins/scheduled-announcements-widget/