RabbitMQ

RabbitMQ is based on a proven platform, offering exceptionally high reliability, availability and scalability along with good throughput and latency performance that is predictable and consistent. It has a compact, easily maintainable code base allowing rapid customisation and hot deployment. There are extensive facilities for management, monitoring, control and debugging and it is supported by a full range of commercial support services and an active community developing packages that extend the core system.

http://www.rabbitmq.com/index.html