The "Active Director" is an Open-Source Directory Administration Toolkit. It is based on Microsoft's ADSI and WMI components and provides a great set of automation tasks for NT Systems and LDAP Directory Services like Active Directory, OperLDAP or Novell Directory Services.
Some interesting features are
* LoginSession & Password Management
* Simplified Property Access and AutoConversion into readable formats
* Change-Management and -RollOut abilities (TemplateSets and RequestSets)
* Data Import/Export Plugins
* Automated logging of each applied change
* Mailbox Inegration (Exchange 5.5 / 2000 / 2003 and POP3)
* FileSystem Integration (Management and Reporting for Files, Directories and ACLs)
* WMI Integration (Remote Workstation and Server Management Tasks)
* Job/Task System
* "Scripted" extention standard