Apache Synapse Enterprise Service Bus (ESB) 

Apache Synapse is designed to be a simple, lightweight and high performance Enterprise Service Bus (ESB) from Apache. Based on a small asynchronous core, Apache Synapse has excellent support for XML and Web services - as well as binary and text formats. The Synapse engine is configured with a simple XML format and comes with a set of ready-to-use transports and mediators.

Apache Synapse 1.2 Release Notes