Websites:

Application Virtualization

http://technet.microsoft.com/en-us/appvirtualization/default.aspx 
http://technet.microsoft.com/en-us/library/bb608292.aspx - - App V. on Technet
http://www.virtualapp.net/ - Free apps and utlities
http://support.microsoft.com/kb/939085 - How to run scripts inside the OSD file
http://blogs.technet.com/softgrid/archive/tags/KB+Article/default.aspx - Latest KB articles on App V. 

DaRT

http://technet.microsoft.com/en-us/library/cc740105.aspx - Debugging tools
http://blogs.msdn.com/winre/archive/2007/01/12/how-to-install-winre-on-the-hard-disk.aspx - How to install WinRE on hidden partition

AIS

http://technet.microsoft.com/en-us/library/bb964349.aspx - Step-by-step guide to deploy AIS

Blogs:

http://www.softgridblog.com/ - Independent blog
http://blogs.technet.com/softgrid/default.aspx - Microsoft Blog

Tools:

http://www.virtualapp.net/sft-explorer.html - SFT Explorer
http://www.immidio.com/resourcekit/ - Toolkit with App V server ping tool

http://technet.microsoft.com/en-us/appvirtualization/dd277292.aspx - App V. resourcekit tools