I have created tiny tiny zimlet for Tungle.me, online scheduling service.
The feature overview is something like this:
You can get the zimlet from this attachment or github below.When you read the email which has someone's tungle.me public url in the message and
click the url on ZimbraWebClient, popup window is displayed on zimbra pages and the widget
provided by Tungle.me is loaded into the window.
By the widget you can check and book the schedule of someone who owns
the public url while checking your own schedule on Zimbra.
bucchi's TungleMe-Zimlet at v0.1 - GitHub
Have a fun with it.