Hi Izzy,
Totara doesn't automatically send a message when activities are added to a course, though that is a great idea for the Suggest Features forum. I am curious if other folks have found workarounds they use? I know a common one is enrolling the audience in the course, creating a discussion forum and auto-subscribing all users to the forum, then posting updates to the forum including a link to the new resource that the user will receive via email.
Cheers!