Messenger Connect allows you to communicate, share, and connect with your Messenger friends on blogs & websites. It is a flexible, yet prescriptive set of APIs to help create intuitive experiences that can be tightly integrated into a website or another app.

Windows Live users Messenger, Hotmail, and SkyDrive users can opt in to provide access to their identity (sign-in, profile, relationships, and additional user data), share updates about the things they’ve done via Messenger social, and chat with their friends, all from within the experience of another website or app.

Messenger Connect enables three core scenarios for websites and app developers:

• Identity – makes it easy for users to sign in and sign up to your web site using their Windows Live ID
• Social distribution – lets users share the things they do on your website with their friends. Activities appear in Messenger, Hotmail, and across Windows Live properties, and other places Messenger social is displayed (including Windows Phone 7 and the very popular Windows Live Messenger iPhone app)
• Realtime shared experiences – lets users share an experience in real time with their friends.

Read more at Windows Live Blog.

Also see Add the Share with Messenger badge to your blog posts.