Best documentation is the companies website:

http://www.postgresql.org/

Pick a mirror.

MySQL uses a db to hold permissions
PostgreSQL uses a text conf file to hold configuration and permissions

I haven't tried PostgreSQL since 7.0.3.  At that time I was working with Snort
(www.snort.org) sniffing a 200Mb Internet connection (not a typo, 200 Mega
bits/s).  MySQL couldn't handle the rate at which alerts were coming in, but
could handle outputting the frontend (ACID: acidlab.sourceforge.net).

PostgreSQL could easily handle the logging, but was slower than molasses for the
web frontend (see the graphs at the above mentioned ACID site).  A page that
took MySQL 30s to load was taking over 8 minutes for PostgreSQL.

> I have been using MySQL for quite some time and feel
> right at home with it..... I would like to begin learning
> postgresql.
> 
> I have just installed it (as a Debian snob, apt-get made that
> pretty brainless), and need a starting point.
> 
> Using MySQL, I am spoiled by mysqlshow, and walking right
> into the mysql db and setting up perms for something I created
> with mysqladmin create 'dbname'. This is my only baseline, and
> would love for someone to point me to some docs that address
> the basics for postgres.