Windows Live Messenger will be the next-generation MSN Messenger. It will have everything you already love about Messenger—your contact list, emoticons, and instant access to your friends via text, voice, and video—plus new ways to connect and share documents with almost magical ease. As always, it will be free to download Messenger and use most of its features.
Windows Live Messenger 8.0 Beta
Thanks to mess.be for the following info:
Microsoft has silently enabled access to the latest Windows Live Messenger Beta for all passports. This means that from now on you won't need an invitation in order to be able to log in.