Most all of the current US Army field manuals (FMs) are available for download directly from the Army at: http://atiam.train.army.mil/soldierPortal/appmanager/soldier/start?_nfpb=true&docGroup=official&_pageLabel=rdlservicespage
Note: Some are restricted access to those with a .gov or .mil address, but many can be downloaded by anyone. BTW, the Army for some reason decided to 'modernize' the numbering system and the 5-series manuals are now 3-series. Generally, though, the older manuals (some of which are available, as mentioned, from globalsecurity.org or FAS.org) are also useful. The newer manuals are more technology intensive than the older ones. It's good knowing the current state of the art though. Keep up the excellent work on SurvivalBlog!
JWR Adds: Anyone in the active military, Reserve, in the National Guard, retired from the military, or that works for a defense contractor can get a Army Knowledge Online (AKO) web account. (See: http://www.army.mil/ako/ ), which will give you access to the entire library of U.S. Army manuals. I presume that AKO accounts might be also available or anyone that is on a Civil Defense team.