INSERT... RETURNING with a function

I've written a straightforward insert function, but using the
RETURNING keyword for the first time. If I try running the test case
I get the error:

ERROR: query has no destination for result data
CONTEXT: PL/pgSQL function "nonauth_users_insert_new_udf" line 7 at
SQL statement

I'm not sure what I need to do to catch the return value as I've
tried a few different combinations and nothing has worked for me so
far. The Insert statement as it is below but outside of a function
works and returns the id. Any input is much appreciated.

I'm running version 8.4

Regards,
Iain

/*test*/
/*
select nonauth_users_insert_new_udf(
'testuser1', 'testuser1(at)example(dot)com', 'xDvTfTOB99mG6zSyMjYtVhUd3P4',
'4DhFLU1YJU5Oz/+XGqh3npn2RJQ'
);
*/

CREATE OR REPLACE FUNCTION nonauth_users_insert_new_udf(
_username varchar
, _emailaddress varchar
, _salt char
, _hash char
) RETURNS int
AS $$
BEGIN

Insert into nonauth_users ( username, emailaddress, salt, hash,
added )
values ( _username, _emailaddress, _salt, _hash, now() )
RETURNING nonauth_users_id;

--the query works this way though
--RETURN currval(pg_get_serial_sequence('nonauth_users',
'nonauth_users_id'));

END;

$$
LANGUAGE plpgsql;