ØMQ. Fastest. Messaging. Ever.

ØMQ looks like an embeddable networking library but acts like a concurrency framework. It gives you sockets that carry whole messages across various transports like inproc, IPC, TCP, and multicast. You can connect sockets N-to-N with patterns like fanout, pubsub, task distribution, and request-reply. It's fast and small enough to be the fabric for clustered products. Its asynchronous I/O model gives you scalable multicore applications, built as asynchronous message-processing tasks. It has over twenty language APIs and runs on most operating systems. ØMQ is open source and fully supported by iMatix.

http://www.zeromq.org/start