The Internet Storm Center shares one handlers toolkit recommendations. This toolkit looks like it will provide you with everything you will need to monitor, troubleshoot and maintain you network. Some us might have personal preferences on AV vendors or other items, but it' s still a very nice list.
ISC publishes Scott' s Toolkit for Windows
I' ve created what I call " Security Kits" on both CD-Rs and now the new FlashRAM memory sticks with a lot of these tools on there 
You never know which neighbor or relative is going to be next on the list to go help out 
Antivirus Tools |-- McAfee Stinger (updated routinely)
|-- Symantec AV Corporate Edition v9 (soon to be v10)
|-- Microsoft Malware Removal Tool (released monthly)
|-- Current Symantec AV Intelligent Updater
Response Kit |-- NetCat (available now at SecurityFocus)
|-- SysInternals AccessEnum
|-- SysInternals AutoRuns
|-- SysInternals Contig
|-- SysInternals DiskView
|-- SysInternals FileMon
|-- SysInternals ListDLLs
|-- SysInternals Page Defrag
|-- SysInternals ProcessExplorer
|-- SysInternals PS Tools
|-- SysInternals RegMon
|-- SysInternals Rootkit Revealer
|-- SysInternals Sdelete
|-- SysInternals ShareEnum
|-- SysInternals Sync
|-- SysInternals TCPView
|-- SysInternals Miscellaneous tools
|-- Heysoft LADS
|-- myNetWatchman SecCheck
|-- Inetcat.org NBTScan
|-- FoundStone BinText
|-- FoundStone Forensic Toolkit
|-- FoundStone Fport
|-- FoundStone Galleta
|-- FoundStone Pasco
|-- FoundStone Rifuti
|-- FoundStone Vision
|-- FoundStone ShoWin
|-- FoundStone SuperScan
|-- WinDump
|-- Nmap
|-- Tigerteam.se SBD (encrypted netcat)
|-- GNU based unxutils (from unixutils.sourceforge.net)
|-- Good copies of windows binaries (netstat, cmd, ipconfig, nbtstat)
Spyware Tools |-- AdAware (updated defs in same directory)
|-- CWShredder
|-- Hijack This
|-- MS AntiSpyWare Beta
|-- Spybot Search and Destroy (updated defs in same directory)
|-- BHO Demon
Security Tools (this is my usual place to dump the .zip or .exe installers) |-- Heysoft LADS (list alternate data streams)
|-- Inetcat.org NBTScan
|-- MS Baseline Security Analyzer
|-- MS IIS Lockdown tool
|-- Sam Spade
|-- SSH Client (SSH.com or Putty)
|-- SysInternals Tools
|-- Foundstone Tools
|-- BlackIce PC Protection
|-- Kerio Personal Firewall
|-- Zone Alarm Personal Firewall
|-- WinPcap
|-- WinDump
|-- Ethereal Installer
|-- Nmap for windows (cli version)
Utilities |-- Adobe Acrobat Reader Installer
|-- CPU-Z
|-- FireFox Installer
|-- Macromedia Flash and ShockWave Installers
|-- Quicktime Standalone Installer
|-- VNC Installer
|-- Winzip Installer
|-- ISCAlert
Service Packs ( on a 2nd CD ) |-- Windows XP SP2
|-- Windows 2000 SP4 (+rpc/lsass critical patches or SRP when released)
|-- Windows 2003 Server SP1
(Some additional CDs I keep around for the Unix geek in me)
Knoppix CD
Helix CD
Note: Any commercial software above that is not freeware/shareware in the list above should be replaced in your toolkit with your company or campus licensed software.