We recently added a new feature to most announcements on the Events page. When you see the red Register button on an event page it means you can indicate your intention to attend. Note this is never used for meetings which always have a signup form that needs to be submitted.
When you add your name to an event it will appear elsewhere in the page along with others that have filled in the short form. This helps us plan for such gatherings. A good example is the form for the Honor Guard for Spc. Matthew Holly on May 21st & 22nd.