The general idea here is to build on the good work already done making Sakai a more social platform by surfacing updates wherever you are.
It would be good to have some visual indicator of unread announcements, updates to, or creation of, assignments and added or updated resources. An icon, facebook style, in the top bar, which changes colour when there's new stuff happened. When you click it you get a flyout list, similar to the Dashboard, where you can click on links to take you to the relevant place, or delete the notification.
Similar to the above, but focused on things like postings on your Profile2 wall, Profile2 messages, connection requests. That kind of stuff. Again, you'll be able to click on it and get a flyout where you'll be able to drill in or delete the notifications.