You can also issue a VACUUM command on the database after each part of the database has been loaded, or even while loading the database. The latter can be done in one of two ways:
See the PostgreSQL documentation for details on the VACUUM command. See also the vacuumdb(1) manual page.
Also, you may want to set the option "fsync = false" in the postgresql.conf file (located in /var/lib/pgsql/data on RedHat). See the PostgreSQL documentation for more information. The performance gain, however, may be minimal with PostgreSQL version 7.1 and higher.