You can buy Redhat Linux CDROM, Debian Linux CDROM or Slackware Linux CDROM which already contains the PostgreSQL in package form (both source code and binaries) from :
PostgreSQL organisation is also selling 'PostgreSQL CDROM' which contains the complete source code and binaries for many Unix operating systems as well as full documentation.
Binaries only distribution of PostgreSQL:
WWW Web sites:
The ftp sites are listed below :-
PostgreSQL source code is also available at all the mirror sites of sunsite unc (total of about 1000 sites around the globe). It is inside the Red Hat Linux distribution in /pub/contrib/i386/postgresql.rpm file.