The Microsoft Active Directory Topology Diagrammer reads an Active Directory configuration using LDAP, and then automatically generates a Visio diagram of your Active Directory and /or your Exchange Server topology. The diagramms may include domains, sites, servers, organizational units, DFS-R, administrative groups, routing groups and connectors and can be changed manually in Visio if needed.
Some Schreenshots:
Download Microsoft Active Directory Topology Diagrammer HERE