Messenger Companion is a browser plugin which lets you quickly share and discover what your friends have shared online. It lets you view the links your friends are sharing, comment on them, and even share something you’ve come across. And if you’ve connected your social networks to Windows Live, Messenger Companion works across all of them.
If you want to check out all recent links shared on a site, all you need to do is use Messenger Companion button in IE. When you join in a conversation, your comment gets posted back to social network your friend used to share link. When you share link through Messenger Companion , it'll update your status in Messenger, and all your friends in Messenger will get an update from you about the link you shared.
Messenger Companion is available to anyone using Internet Explorer 7 or Internet Explorer 8. You can get it now by installing the Windows Live Essentials beta.
via Inside Windows Live