The ISA Server 2006 SP1 was release today (couple of minutes ago) and you can download from the link below: http://www.microsoft.com/downloads/details.aspx?FamilyId=D2FECA6D-81D7-430A-9B2D-B070A5F6AE50&displaylang=en

 

We do have some good articles out there already that talks about the functionalities of this release, review some of them:

 

Jim Harrison reveals ISA Server 2006 SP1

ISA Server 2006 SP1 Demos by Yuri Diogenes

Your New ISA Firewall: ISA 2006 Service Pack 1 (Part 1) by Tom Shinder

ISA Server 2006 Service Pack 1: New features and enhancements by Marc Grote