.NET Active Directory Wrapper    
Access Active Directory From Your C# or VB .Net Code
 

Active Directory
Introduction
Objects
Object Properties

DirectoryServices Namespace
Introduction
DirectoryEntry Class

How to .. in C# .NET
Create User
Disable User
Enable User
Authenticate a User
Change User Password
Get DirectoryEntry of a user
Get Users in a Group
Get Object Property

Other Resources
References

Creating a New User in Active Directory

public static DirectoryEntry CreateNewUser(string cn)
{
//set the LDAP qualification so that the user will be created under the Users
//container
string LDAPDomain ="/CN=Users," + GetLDAPDomain();
DirectoryEntry oDE= GetDirectoryObject(LDAPDomain);
DirectoryEntry user = oDE.Children.Add("CN=" + cn, "user");

//Must commit changes to initially create user
user.CommitChanges();

oDE.Close();
oDE.Dispose();

return user;

}