PL/SQL Packages DBMS_AQ

Add a message (of a predefined object type) onto a queue or dequeue a message.
Oracle's Advanced Queuing.

See:
Oracle9i Application Developer's Guide - Advanced Queuing 

Related Views:

 DBA_QUEUES           ALL_QUEUES           USER_QUEUES 
                                                        QUEUE_PRIVILEGES  
 DBA_QUEUE_SCHEDULES                       USER_QUEUE_SCHEDULES 
 DBA_QUEUE_TABLES     ALL_QUEUE_TABLES     USER_QUEUE_TABLES