docs about security

Hi!

I am resending a plea for some good security docs, or locations
thereof.  I have been wrestling with security on Postgres for some
time, and have finally given up for a time.  Is there a chance that
someone could write a good tutorial, or a chapter in a book, that can
explain the various aspects of security on Postgres.

The reason that I am asking, is because I have been trying to see if
Postgres would/could be a replacement for our 30+ databases(access +
sql server).  From the understanding that I get from what I read it
doesn't look like I can do the security scheme that I want.  (I have
great respect for all of you who are working on a great product, but
as of now, I can't wrap my brain around your security scheme...:(  )

Thanks for letting me vent,

Speeves