… and/or domain functional level?  There is a table on the following TechNet page that outlines this info.  It has been a re-occuring question in my recent trips!  Note that the domain functional level is the important factor for 2008, as that enables new features including fine grained password policy.

http://technet2.microsoft.com/windowsserver2008/en/library/34678199-98f1-465f-9156-c600f723b31f1033.mspx?mfr=true