Microsoft Office Live Meeting is a web conferencing service that connects and engages participants in online meetings, training, and events. Live Meeting incorporates video, voice, instant messaging, document sharing and collaboration, virtual white board, and more. Participants can share what is on their screens, collaborate on documents, and deliver or watch presentations. Sessions may be recorded.
You can launch an instant, ad hoc meeting using the 'Meet Now' option within the Live Meeting client or Office Communicator.
Using Outlook's Conferencing Add-in, you can schedule a meeting, or a Communicator conference call, in advance of a specific date and time.
See it in action - take Microsoft's quick tour.