Quick Notice plugin by Shaon will help the admin to publish highlighted notice on WordPress site header. Any message like offline notice, update notice, tweets, special offers, latest post can be set to attract visitors in 1st sight.
Features
Custom Webfont support
Custom background css option
Fully customizable apearance and font
Click and Impression Tracking option coming soon
Download and info: http://wordpress.org/extend/plugins/quick-notice/