Announcements are a great way to keep your site fresh and keep visitors interested and returning to your site for more information. Announcements can act on their own and be tied into an RSS feed for distribution on Twitter, Facebook, etc. They can also be tied into a calendar and events that people can register for or add to their calendar. If you have something to announce, even if it's just once a month, add it to your website and tell your customers about it.
If your company is event-based or attends a lot of events, a calendar is a great addition to your website. Display your calendar on your website, use it as an appointment tool, or get subscribers and alert them as new events are added. Calendars can even sync to your desktop applications ,allowing you to update your calendar without logging in to your website.
WARNING: Calendars and announcements are also a great way to show your customers you haven't updated your website in a while. So stay committed to updating your announcements on a regular basis.