Tips and Alerts Zimlet
This Zimlet gives sites the ability to present all logged-in users with a broadcast alert. In addition, users can receive a "tip of the day" at login or when they left-click on the Zimlet.
No action is necessary on the end-user's part, but the site must set up a separate REST server (bundled with the Zimlet code) where the Tips, Alerts, and Settings are stored. See the included README for details.