For the GUI and CLI solutions to mean much to you, you need access to the tools that are used in the examples. For this reason, in the majority of cases and unless otherwise noted, I used only tools that are part of the default operating system or available in the Resource Kit or Support Tools. There are two exceptions to this rule that I'll explain shortly.
The Resource Kits for Windows 2000 Server and Windows Server 2003 are invaluable sources of information, and provide numerous tools that aid administrators in their daily tasks. More information on the Resource Kits can be found at the following web site: http://www.microsoft.com/windows/reskits/. Some tools are freely available online, but others must be purchased as part of a Resource Kit. The Windows 2000 Support Tools, which are called the Windows Support Tools in Windows Server 2003, contain many "must have" tools for people that work with Windows Server. The installation MSI for the Windows Support Tools can be found on a Windows 2000 Server or Windows Server 2003 CD in the \support\tools directory.
Even though many of the same tools are available in both the Windows 2000 Support Tools and Windows Server 2003 Support Tools, several have been enhanced in the latter version including LDP, Dsacl, and LDIFDE.
The biggest source of tools that I use that don't come from Microsoft can be found on the Sysinternals web site: http://www.sysinternals.com/. Mark Russinovich and Bryce Cogswell have developed a suite of extremely useful tools that every Windows Server system administrator should be familiar with. These tools are free and they often come with complete source code for the tool.
Another good source of tools, especially for Active Directory, is Joe Richards' Joeware site: http://www.joeware.net/. Joe wrote many of his tools, some in executable form and others in Perl, to help in daily system administration tasks, so they are all very practical and useful. And like Sysinternals, most are free.