Microsoft has released ISA Server 2006 Beta for download

Thank you for your interest in evaluating ISA Server 2006 Beta. You can now try ISA Server 2006 Beta by downloading the trial software from the links below. The fully functional trial software offers you the opportunity to experience the new features and functionality of ISA Server 2006. The trial automatically expires 180 days after you install it on your servers.

To receive the free trial software of ISA Server 2006 Beta, click the link below for the desired edition. This link will take you to the ISA Server 2006 Beta registration form. After you submit the form, you will receive a link to the download location as well as links to other helpful resources.

Read more
System requirements
Download ISA Server 2006 Beta - Standard Edition
Download ISA Server 2006 Beta - Enterprise Edition