fonglh

Easily create an announcements news ticker on your website. Put up new announcements just like how you would put up a blog post. Use the [announcements] shortcode to display all your announcements in a page or post.
Customize the look of your ticker from the WordPress administration screens. An options page allows you to change the colours and size.

Announcements Ticker

Provides a shortcode and custom post type to display announcements using a jQuery news ticker.

eisenivan

A lightweight plugin that allows you to place a sitewide alert message in the header of your site. There are options to include a default set of styles (based on Twitter Bootstrap), center your alert, and switch the style class.

Summits Alert

A lightweight plugin that allows you to place a sitewide alert message in the header of your site.

Announcements Ticker vs Summits Alert