Among the flurry of email and notifications, here are some tools you can use to help your official, not-to-be-missed, announcements stand out.
Sakai Announcements
A dedicated one-way tool for you to use to contact all students in your Sakai site.
Sakai Forums
Generally used for discussions, you can set aside a forum for official announcements.
Google Groups
Generally used for group discussion, careful formatting and standards can help official announcements stand out from the general conversation.
Explore the VIRTL documentation on Communicating Official Announcements for more information on how to use these tools.