Upgrading your Virtual Infrastructure Management Components
http://download3.vmware.com/vsphere/vsphere-migration-part1.html
ESX Host Migration Methods
http://download3.vmware.com/vsphere/vsphere-migration-part2.html
Virtual Machine Upgrades
http://download3.vmware.com/vsphere/vsphere-migration-part3.html
Implementing vSphere Licensing
http://download3.vmware.com/vsphere/vsphere-migration-part4.html