Mil specs can be downloaded for free–

• Mil specs as well as some other federal specs can be
  downloaded in Adobe Acrobat ‘.pdf’ format from
  https://quicksearch.dla.mil/
   It could change, but as of Jan 2013 it’s still free.

ASTM, ANSI, ISO, etc. are copyrighted ‘commercial’ specs, so
you’ll need credit card in hand–

• ASTM offers their ‘Webdoxx’
  system whereby you can immediately download ‘.pdf’ (Adobe Acrobat
  Reader) copies of specs (after paying by credit card).

• A commercial site is document-center.com