How do you show SQL executing on an Oracle database? How can you show the SQL that is currently executing on an oracle db?

Extra information that would be useful would include user, session id etc.
Most of the info is available in v$session ... and the SQL Text can be grabbed from v$sql or v$sqltext_with_newlines...

Here is a query that I often use that formats In-flight SQL, longest running at top. 

-- In Flight SQL 
SELECT nvl(ses.username,'ORACLE PROC')||' ('||ses.sid||')' USERNAME,
       SID,   
       MACHINE, 
       REPLACE(SQL.SQL_TEXT,CHR(10),'') STMT, 
      ltrim(to_char(floor(SES.LAST_CALL_ET/3600), '09')) || ':'
       || ltrim(to_char(floor(mod(SES.LAST_CALL_ET, 3600)/60), '09')) || ':'
       || ltrim(to_char(mod(SES.LAST_CALL_ET, 60), '09'))    RUNT 
  FROM V$SESSION SES,   
       V$SQLtext_with_newlines SQL 
 where SES.STATUS = 'ACTIVE'
   and SES.USERNAME is not null
   and SES.SQL_ADDRESS    = SQL.ADDRESS 
   and SES.SQL_HASH_VALUE = SQL.HASH_VALUE 
   and Ses.AUDSID &lt;&gt; userenv('SESSIONID') 
 order by runt desc, 1,sql.piece;