Government Attic has also just posted a somewhat less declassified NSA compendium from 1993: A Collection of Writings on Traffic Analysis, http://www.governmentattic.org/8docs/NSA-TrafficAnalysisMonograph_1993.pdf"
Link to Original Source
I never cheated an honest man, only rascals. They wanted something for nothing. I gave them nothing for something. -- Joseph "Yellow Kid" Weil