Windows Live Messenger supersedes the current MSN Messenger with new branding and a host of new features, including voice-over-IP calls, video calls, folder sharing, and instant updating of contact information. Microsoft also boasts about the upcoming ability to chat with users of Yahoo! Messenger from Windows Live Messenger, although that feature isn't available yet. Users can grab Windows Live Messenger from Microsoft's Live Services website right here.
In addition to Windows Live Messenger, Microsoft has a host of other Windows Live products awaiting official release. Those include a Live.com web portal, a Live Local mapping service, and Windows Live Search—Microsoft's planned Google-killer. CNet has put up a handy chart that lists various Windows Live services, their current status, and the competing services and companies they're poised to challenge.