Find long running SQL queries

Question:  How do I query to find long-running queries?  I want to identify SQL queries that are running for an inordinate amount of time.

select * from
(
  select
     opname,
     start_time,
     target,
     sofar,
     totalwork,
     units,
     elapsed_seconds,
     message
   from
        v$session_longops
  order by start_time desc
)
where rownum <=1;

DECLARE
l_rindex PLS_INTEGER;
l_slno PLS_INTEGER;
l_totalwork NUMBER;
l_sofar NUMBER;
l_obj PLS_INTEGER;
BEGIN
l_rindex := DBMS_APPLICATION_INFO.set_session_longops_nohint;
l_sofar := 0;
l_totalwork := 10;
WHILE l_sofar < 10 LOOP
-- Do some work
DBMS_LOCK.sleep(5);
l_sofar := l_sofar + 1;
DBMS_APPLICATION_INFO.set_session_longops(
rindex => l_rindex,
slno => l_slno,
op_name => 'BATCH_LOAD',
target => l_obj,
context => 0,
sofar => l_sofar,
totalwork => l_totalwork,
target_desc => 'BATCH_LOAD_TABLE',
units => 'rows');
SEE CODE DEPOT FOR FULL SCRIPT
END LOOP;
END;
/

set wrap off
col elapsed_time_delta format 9999999999
col plan_hash_value    format 9999999999
col seconds            format 99999
col executions_total   format 99999999

select
   stat.sql_id, 
   plan_hash_value,
   rpad(parsing_schema_name,10) "schema",elapsed_time_total/1000000 "seconds",  
   elapsed_time_delta,disk_reads_delta,
   stat.executions_total,
   to_char(ss.end_interval_time,'dd-mm-yy hh24:mi:ss') "endtime", 
   rpad(sql_text,40) text,ss.snap_id
from
   dba_hist_sqlstat  stat,
   dba_hist_sqltext  txt,
   dba_hist_snapshot ss
SEE CODE DEPOT FOR FULL SCRIPT
where
   stat.sql_id = txt.sql_id
and
   stat.dbid = txt.dbid
and
   ss.dbid = stat.dbid
and
   ss.instance_number = stat.instance_number
and
   stat.snap_id = ss.snap_id
and
   parsing_schema_name not like 'sys%' 
and
   ss.begin_interval_time >= sysdate-40
and
   stat.elapsed_time_total/1000000 > 20
order by
   elapsed_time_total desc;