Military Resources: Research & Technology
Center for Defense Information
"America's foremost independent military research organization." The CDI monitors international military affairs as well as domestic.
Virtual Defense Library
From the Defense Technical Information Center which offers searchable collections including technical reports.
Designed for professional contractors, these sites offer useful information to casual researchers. Current projects and equipment catalog sections, as well as professional information and industry organizations, will be of special interest.
Like Railway Technology, this site is designed for professional contractors but offers interesting information to any technophile or armchair general.