Hi dear friends.
The database list in openerp login page is provide by the method def exp_list(self,document=False) which is in /openerp/service/web_services

def exp_list(self, document=False):
        if not tools.config['list_db'] and not document:
            raise openerp.exceptions.AccessDenied()
        chosen_template = tools.config['db_template']
        templates_list = tuple(set(['template0', 'template1', 'postgres', chosen_template]))
        db = sql_db.db_connect('postgres')
        cr = db.cursor()
        try:
            try:
                db_user = tools.config["db_user"]
                if not db_user and os.name == 'posix':
                    import pwd
                    db_user = pwd.getpwuid(os.getuid())[0]
                if not db_user:
                    cr.execute("select usename from pg_user where usesysid=(select datdba from pg_database where datname=%s)", (tools.config["db_name"],))
                    res = cr.fetchone()
                    db_user = res and str(res[0])
                if db_user:
                    cr.execute("select datname from pg_database where datdba=(select usesysid from pg_user where usename=%s) and datname not in %s order by datname", (db_user, templates_list))
                else:
                    cr.execute("select datname from pg_database where datname not in %s order by datname", (templates_list,))
                res = [tools.ustr(name) for (name,) in cr.fetchall()]
            except Exception:
                res = []
        finally:
            cr.close()
        res.sort()
        return res

Best reagrds.