Mule is an Enterprise Service Bus (ESB) messaging framework. It is a scalable, highly distributable object broker that can seamlessly handle interactions with services and applications using disparate transport and messaging technologies.

Jencks is a lightweight JCA container which is easy to deploy inside Spring to provide inbound and outbound messaging using APIs like JMS, JAX-RPC, JBI and JCA CCI as well as providing an XA based pooling mechanism for JDBC and easy integration of Geronimo's TransactionManager with Spring.

Lingo is a lightweight POJO based remoting and messaging library based on Spring's Remoting which extends it to support JMS. Lingo can support a wide range of message exchange patterns including both synchronous and asynchronous message exchange. Lingo is an ideal technology to cluster your POJO services to achieve load balancing across many servers and automatic failover. Lingo is high performance and works great in server centric environments as it can work with JCA to cleanly integrate with thread, connection and session pooling as well as handing of transactions, retry and exception handling.

XStream is a simple library to serialize objects to XML and back again. Features: Ease of use, no mappings, performance, clean XML, no modifications to classes, integration with XML libraries, full object graph support, customizable conversion strategies.

A wire protocol designed for cross-platform messaging