Check out the newest content in the TechNet library for Hyper-V:
Live Migration Step by Step Guide:
http://technet.microsoft.com/en-us/library/dd446679.aspx
What’s New for Hyper-V in R2:
http://technet.microsoft.com/en-us/library/dd446676.aspx
Hyper-V Virtual Machine Snapshots: Frequently Asked Questions:
http://technet.microsoft.com/en-us/library/dd560637.aspx
Tony Soper alerted that there is some new content in the TechNet library for Hyper-V that is worth checking out: Live Migration Step by Step Guide, What’s New for Hyper-V in R2, Hyper-V Virtual Machine Snapshots: Frequently Asked Questions