AD Topology Diagrammer
Looks like a cool tool… haven’t had the time to test it… yet.
The Microsoft Active Directory Topology Diagrammer reads an Active Directory configuration using ActiveX Data Objects (ADO), and then automatically generates a Visio diagram of your Active Directory and /or your Exchange 200x Server topology. The diagramms include domains, sites, servers, administrative groups, routing groups and connectors and can be changed manually in Visio if needed.