If you have Xobni installed, you can send invites to your friends from within the application.
Read the coverage on TechCrunch, GigaOm, and our very own Xobni blog.
This starts an exciting new phase for Xobni where we're become available to more and more users. We're spreading email happiness. If you have Xobni installed, don't forget to invite your friends!
Update: Lifehacker: Supercharge Outlook with Xobni
Update 2: MIT Technology Review:: Yahoo's Plan for a Smarter In-Box : "Yahoo isn't alone in its desire to reshape e-mail."