Windows System Administration
Windows System Administration
and Security
SANS.org I can recommend the SANS Windows Security course (1 week).  Useful (I am tempted to say essential) for both Windows and Unix sysadmins.  Presentation is by independent ITSec professionals; this is not a vendor course.
Active Directory
AD is core to Windows server/domain security, user, group and software management.  Learn all about it... from several viewpoints.
Windows Scripting Examples
Over 1900 examples of Windows scripting for administrative tasks
Windows Commandline Interfaces
CMD.EXE Enhanced Windows commandline replacement for COMMAND.COM.  Most definitely worth learning thoroughly if you plan to do any powerful scripting or admin tasks under Windows.
Cygwin BASH
If you have Cygwin installed on your system, you can have the interactive power of the BASH shell, run shell scripts, and use your favorite Unix commands in conjunction with DOS/Windows commands.

With Cygwin installed, you can also run Unix commands from CMD and from BAT files, mixing, matching and piping as you see fit.
Windows tips and tricks I use  click here
Scriptable Network Clients
wget
curl
Scriptable HTTP/HTTPS clients.  Their output can be used to feed into Windows tools like Excel.  Wget is able to download entire sites recursively.

rsync

Keep files and directories synchronised between hosts, securely
Emulation & Interoperability Tools
click here
Performance and Tuning click here