Insert Data and autonumeric field

Hi everybody,
I need to insert a row in a table and get the Id of this row ( My primary key ).

Example:

INSERT INTO table1 (date, field2, field3) VALUES (now,'value2','value3');
SELECT last_value FROM seq_table1;

I'm running each command apart. My application retrieves the last_value and uses it in another command:

INSERT INTO table2 (pk1, field1, field2, field3) VALUES ( last_value_variable, 'value1','value2','value3');

PROBLEM: Many clients are getting duplicated IDs.

What is the best way of doing this?

I tried a function:

CREATE OR REPLACE FUNCTION fu_insertrow(int4, text)
RETURNS int4 AS
$BODY$
DECLARE
i_lastvalue INTEGER;
BEGIN

INSERT INTO table1 (date, field1, field2) values (now(),$1,'$2');
SELECT i_lastvalue INTO i_lastvalue from "seq_ChamadaId";
RETURN i_lastvalue;

END;
$BODY$
LANGUAGE 'plpgsql' VOLATILE;

Using this function:

SELECT fu_insertrow(value2, value3);

The app gets the return value of the function above and uses it in my insert:
INSERT INTO table2 (pk1, field1, field2, field3) VALUES ( function_return_variable, 'value1','value2','value3');

Suggestions?

Thanks,
André Guergolet