Network Virtualization Introduction – VMware NSX
http://www.vmware.com/products/nsx/nsx-webinar.html
The VMware Networking and Security Business Unit (NSBU) has a great webinar series that provides an interactive 101 presentation on what NSX is. This presentation is hosted by the systems engineers from the NSBU including myself, I highly recommend it as a foundation for understanding network virtualization and VMware NSX capabilities!