Message Queues
ActiveMQ or RabbitMQ or ZeroMQ or ...
has some good discussion and some excellent links, many copied below
Message Queue Evaluation Notes
by Linden Labs, who were looking for an infrastructure for Second Life
Comparing OpenDDS and ZeroMQ Usage and Performance
is a puff piece for OpenDDS, but pretty impressive (and OMG isn't dead!)
StompConnect
is a STOMP server which wraps a JMS provider
0MQ - The Guide
is a terrifically readable extended tutorial and cookbook for 0MQ