HornetQ is a multi-protocol, embeddable, high performance, clustered, asynchronous messaging system. HornetQ is an example of Message Oriented Middleware. It includes an extensive, easy-to-understand user-manual and quick-start guide and over 65 ready-to-run examples out of the box, demonstrating everything from simple JMS usage to complex clusters of servers and more exotic functionality. Its elegant POJO based design has minimal third party dependencies. You can run HornetQ as a stand-alone messaging broker, run it in integrated in your favorite JEE application server, or run it embedded inside your own application. Its journal provides high persistent messaging performance. Automatically switching into native mode when running on Linux, it uses asynchronous IO to provide persistent messaging rates that can saturate the write throughput of a disk. Its pluggable transport system uses JBoss Netty out of the box to provide high performance and scalability on the wire.
Syncless is an experimental, lightweight, non-blocking (asynchronous) client and server socket network communication library implemented in Stackless Python 2.6. It contains an asynchronous DNS resolver (using dnspython) and an HTTP server capable of serving WSGI applications. It aims to be a coroutine-based alternative of event-driven networking engines (such as Twisted and FriendFeed's Tornado). It is already about that fast, but it has fewer features and is less stable now.