The US National CAD Standard as implemented by the military is located at the CAD/BIM Technology Center.  It is called the A/E/C CAD Standard.  What has changed recently? Drawing Templates have been grouped together making it much more convenient to download and deploy.  The web page containing the links is date stamped 09/07/2010.  Groupings are as follows:

Architectural/Structural/Mechanical/Electrical/Plumbing Template files (1.9 Mb ZIP) 
CIVIL/SURVEY MAPPING File Templates (736.2 Kb ZIP)

How to find the CAD/BIM’s NCS 4.0 downloads. 

When you get the the CAD/BIM Technology Center web page the left hand margin contains links.  Choose Capabilities > Computer Aided Design (CAD).  You will see a Links category and a Documents category.  Expand the folder list under Documents.

What has changed?

Nothing really except the grouping of disciplines for a more convenient download of drawing templates and .lin files.   Click the image to get a glimpse of how the page is laid out.

What’s the diff between NCS 4.0 (http://www.buildingsmartalliance.org/index.php/ncs ) and the A/E/C CAD Standard? 

The Center receives a lot of calls and e-mails asking what is the difference between the NCS and the A/E/C CAD Standard. Basically, the A/E/C CAD Standard is a Department of Defense implementation of the NCS, with service-specific needs added. For instance, the NCS does not include detailed layers on items such as airfields and levees. However, these geospatial features are needed for both Air Force and USACE Civil Works CAD files. This is where the A/E/C CAD Standard fits in, as these items are covered and named so that they follow layer naming conventions established by the NCS.

For your convenience I have clipped out the answer to the above question “Whats the diff…” from this 3 page document https://cadbim.usace.army.mil/MyFiles/2010article_mcgcomments.pdf .  You can find this document and others on the home page of the CAD/BIM Technology Center.