MOM = Message Oriented Middleware.
MQ = Message Queue.
Idea is in buildind asynchronics protocols, based on sending and receiving of messages throught queueis. In some situation this is really good approach.
Most know implementations:
IBM MQ Series.
MSMQ from Microsoft.
(good introduction article:http://my.execpc.com/~gopalan/mts/msmq.html)
JMS [Java Message Service]
In CORBA world
services implements related functionality.