Pattern-Oriented Software Architecture: A System Of Patterns by Frank Buschmann, Regine Meunier, Hans Rohnert, Peter Sommerlad, and Michael Stal. Wiley, c1996, (ISBN 0471958697).
The Siemens Gang prefers POSA as the official (read most used) acronym for their book.
The book has three categories of patterns: architectural patterns, design patterns, and idioms. The architectural patterns are:
Layers
Broker
Reflection (aka Open Implementation, Meta Level Architecture)
Frankly, I hate both the buzzword-compatible title of our book as well as the acronym Po Sa. Only, both were the better choice considering alternatives. For instance, people proposed Gang Of Five (Party Of Five?) as a nickname for us. Imagine the confusion this can cause (and caused in my brain when I heard it for the first time!) -- Hans Rohnert
Hmmm, so which of the authors thought it was cute that
"Patterns of
Software
Architecture --
A System of
Patterns" has an acronym that's a palindrome?
-- Jim Coplien
Would that be an acronome?
Someone has recommended looking at the Siemens Pattern Galaxy, at
pizpalue.zfe.siemens.de 
[Broken Link]
Sadly a lot of people noticed that this page can't be found by their browsers. On www.longsoft.de [Broken Link] it states (in German), that this page sadly is only reachable from within Siemens.
See original on c2.com