Snapshots are a feature of Active Directory introduced in Windows Server 2008. In order to use them you don't have to have your domain running in Windows Server 2008 mode but you do need at least one Windows Server 2008 or Windows Server 2008 R2 domain controller.
Snapshots are created and manipulated using the ntdsutil.exe command line utility. Once you have an Active Directory snapshot you can export it using dsamain.exe (otherwise known as the Active Directory database mounting tool), and you can then interact with it using any Active Directory or LDAP tool.

Offline domain join is a new process that computers that run Windows 7 or Windows Server 2008 R2 can use to join a domain without contacting a domain controller. This makes it possible to join computers to a domain in locations where there is no connectivity to a corporate network.
First the computer account is created or provisioned on the domain controller and the resulting information is stored in the metadata, and then this information is transferred to the joining computer. The workstation then performs the joining part without having the connectivity with the domain controller.
You need to use Djoin.exe on the domain controller to accomplish above. Please use Djoin.exe /? to see the syntaxes.
An example is given below:
Djoin.exe /provision /domain Name_Of_the_Domain_To_Be_Joined /machine Client_Computer_Name /savefile File_Name.txt

Windows Server 2008 Active Directory is a feature called fine grained password policies (FGPPs).In Server 2000 and 2003.

Active Directory domains, you could apply only one password and account lockout policy to all users in the domain, so if you wanted different password and account lockout settings for different sets of users, you had to either create a password filter or deploy multiple domains. In Windows Server 2008 you can use fine grained password policies to specify multiple password policies, apply different password restrictions and account lockout policies to different sets of users within a single domain. FGPPs become available once the domain has been promoted to Windows Server 2008 Domain Functional Level.

To store fine grained password policies, Windows Server 2008 includes two new object classes in the Active Directory Domain Services schema Password Settings Container and Password Settings. The Password Settings Container object class is created by default under the System container in the domain. It stores the Password Settings objects (PSOs) for that domain. You cannot rename, move, or delete this container. Policies you create are represented by Password Setting Objects within Active Directory. To manage PSOs you need to use ADSI Edit or an LDIF file.

Restart able AD DS is a feature in Windows Server 2008 that you can use to perform routine maintenance tasks on a domain controller, such as applying updates or performing offline defragmentation, without restarting the server.

While AD DS is running, a domain controller running Windows Server 2008 behaves the same way as a domain controller running Microsoft® Windows® 2000 Server or Windows Server 2003.

While AD DS is stopped, you can continue to log on to the domain by using a domain account if other domain controllers are available to service the logon request. You can also log on to the domain with a domain account while the domain controller is started in Directory Services Restore Mode (DSRM) if other domain controllers are available to service the logon request.

• Global Object Access Auditing.
• Reason for access" reporting.
• Advanced audit policy settings.