I have also scrounged the Internet looking for examples of Postgres being used in government, preferably in 24x7 capacities.
I find googling for vendors who are known to use PostgreSQL and searching for people's resumes is a good way to find descriptions of Government projects along with contacts for references. Here's a couple that look interesting.
US Navy, Northrop Grumman
Use PostgreSQL in the Navy Enterprise Portal and the Fleet Numerical Meteorology and Oceanography Center(FNMOC) Portal:
http://kennethbowen.com/kbresume.html
" Develop J2EE application to store user profiles for the Navy Enterprise Portal and the Fleet Numerical Meteorology and Oceanography Center(FNMOC) Portal using JBoss application server and PostgreSQL database. "
DOD, USGS, USDA, Army Corp of Engineers, Navy, through a company called Sanz:
http://postgis.refractions.net/pipermail/postgis-users/2005-March/007399.html
Sanz manages "tens of terrabyte datasets of raster and vector data for the DOD, USGS, USDA, Army Corp of Engineers, Navy, etc." using postgresql and postgis
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