Some might find this useful for creating PostGIS databases without having to be postgresql superusers. The idea is to create a template_postgis database, install plpgsql and postgis into it, and then use this database as a template when creating new PostGIS databases.

$ psql template1
\c template1
CREATE DATABASE template_postgis WITH template = template1;
 
-- set the 'datistemplate' record in the 'pg_database' table for
-- 'template_postgis' to TRUE indicating its a template
UPDATE pg_database SET datistemplate = TRUE WHERE datname = 'template_postgis';
\c template_postgis
CREATE LANGUAGE plpgsql ;
\i /usr/share/postgresql/contrib/lwpostgis.sql;
\i /usr/share/postgresql/contrib/spatial_ref_sys.sql;
 
-- in a production environment you may want to 
-- give role based permissions, but granting all for now
GRANT ALL ON geometry_columns TO PUBLIC;
GRANT ALL ON spatial_ref_sys TO PUBLIC;
 
-- vacuum freeze: it will guarantee that all rows in the database are
-- "frozen" and will not be subject to transaction ID wraparound
-- problems.
VACUUM FREEZE;

Now non-superuser’s can create postgis db’s using template_postgis:

createdb -h host-name my_gisdb -W -T template_postgis