To set a static ARP entry, the command used to be arp -s IP MAC, but on Server 2008 R2 and perhaps others back to Windows 7/Server 2008, this command may not work even if Run as Admin. However, the netsh commands in this Q&A provide alternate syntax that does work for the same purpose.
Free tools like Xirrus Wi-Fi Inspector and the Xirrus Wi-Fi Monitor Gadget for Windows 7 with links to other third-party systems/network admin tools. Very cool!
Person recently had occasion to put a routing switch into a DMZ environment, which prompted him to research how to harden it. This document explains some of the steps he's taken to ensure the switch is secure.
Freeware GUI for Windows Time Service configuration, allowing full control of time sync graphically but still using the Windows sync tools (unlike many tools that do the clock sync and set your clock directly). Works with Windows XP/2003/Vista/2008 32-bit and 64-bit.