I have discovered that finally there is an organization that is recognized as standard for protocol: AMQP. They offer examples of products that implement their protocol.
A couple of interesting solutions aligned with this protocol are:
- Rabit MQ: they have documentation and useful examples. http://www.rabbitmq.com/getstarted.html
- QPID, Apache: http://qpid.apache.org/
- Red Hat Enterprise MRG: http://www.redhat.com/products/mrg/
I have to see how the communities evolve and the open source solutions grow. Too early to understand what is the leader solution.