Microsoft Windows Update Services (WSUS)
http://www.wsus.info/
http://www.wsuswiki.com/
Note, by the end of 08/2005, I will have replaced our two SUS servers with WSUS.  Check back.  This will handle Windows and Office updates.

Microsoft Software Update Services (SUS)
08/2005 update - this has been replaced with WSUS.
This will allow you to centrally manage critical patches to MS windows products.  Read the deploy guide!

Main MS pagehttp://www.microsoft.com/windowsserversystem/updateservices/evaluation/previous/default.mspx
http://www.susserver.org/ This is run by a Microsoft MVP - excellent reference for SUS.

SUS Periodic Changes http://support.microsoft.com/default.aspx?scid=kb;en-us;894199 "Changes in SUS 1.0 content are tracked through KB article 894199 … We will try to update that KB article shortly after releasing, modifying or retiring updates in SUS." Quote from Don Cottam from Microsoft 5/5/2005 on the PatchManagement.org list.

Researching
I use this website to research how a patch may affect my environment.   http://archives.neohapsis.com/.  "A collection of public mailing lists and vendor announcements that have been converted to HTML for community use and "archiving" purposes".