Understanding 8.4 new WITH syntax

I've seen a few examples about 8.4 Implementation of WITH syntax.

However, I don't fully understand how the various parts of this kind
of query work together as a whole.  Does anyone know of any good
resources that explain it well?

--
Regards,
Richard Broersma Jr.

Visit the Los Angeles PostgreSQL Users Group (LAPUG)
http://pugs.postgresql.org/lapug