Previously only available as an "invite only" test, Microsoft has launched a publicly available beta version of Windows Live Messenger, an instant-messaging program that now features video conversation and support for VoIP calling.
The program, available from the Windows Live Ideas site, is the next generation of Microsoft's long-running Messenger service. New features include the previously-mentioned VoIP support, plus video chat if you have broadband and a webcam. It will also feature file sharing of sorts via Sharing Folders - share personal photos, documents, and files with your Messenger contacts by dragging files onto a contact name.
In addition, there's continually updated contact information for all your contacts, plus the ability to store up to 600 contacts (for the popular people out there). There will also be offline instant messaging, so if your contact isn't online, they'll get your message as soon as they sign on.
It is still a beta version, but you can download it now for free.