Adding a dynamic Skype sig to Mail.app
A post on the Skype blog describes 
how to add a dynamic Skype icon to a signature in Mail.app, which lets other know whether you are currently available or not.
It basically follows the same method as you use to insert any HTML signature into Mail.app, or a CSS signature or a rotating FeedBurner signature.
Tags: Apple Mail, Apple Mail Tips, css, email, HTML, mail.app, signatures, skypeRelated posts