Centralized users management, policies (group policies / GPO), shared folders, ...
Sign your certificates to secure servers in your local network (or intranet), ...
Management of one or more domain names in a local network (or intranet).
Distribution of IP addresses to allow client computers to communicate over the network. Also used for PXE.
NAT and network routing
Turn your server into a router to filter Internet access.
PXE (boot on the network)
Create a PXE server to boot your PC clients on Live CD, bootable disks, ... over the network.
WDS (Windows deployment services)
Install many identical copies of Windows. Sysprep can be used to generalize a Windows installation.
Terminal Server (thin clients)
Boot thin clients on a terminal server. These clients will not need hard drives to operate.
Terminal Server (RemoteApp)
Eg : use applications published on a server by using Remote Desktop Services.
Eg : install virtualization solutions (such as Citrix XenDesktop, Citrix PVS, 2X ThinClientServer, ...) designed for Windows Server.
Shared folders and NTFS rights
Share server folders and use the Active Directory to manage NTFS security of these shares.
Coming soon : management of group policies, ...