Is there a module to show a quick message to a user or role? Is there a module to send a user or users having a role a message like the one that is currently on top of this site (The Drupal Answers 2012 community moderator election is underway — nominations now being accepted.")?

I don't need a message box like the one that Private message module provides, but a quick message.
See the User Alert Module. This module provides a simple way to show a short-term urgent message on the website. Think of CNN Breaking News, when they show a short message the top of the site (or the 'Welcome!' style messages at StackExchange websites). This module works for both anonymous and authenticated users by using a cookie, and recording actions in the database. This solves the need to show messages independent of the users authenticated status. With User Alerts, you can: Alert users about breaking news, or a special same-day sale for ecommerce. You can also set expiration timers for alerts (1 hour, 3 hours, Never, etc) (Drupal 6 Only, D7 requires Scheduler).