ActiveMQ
ActiveMQ is an open source, Apache 2.0 licensed, high performance Messaging Fabric consisting of a scalable cluster of Message Brokers and a complete JMS 1.1 provider which integrates seamlessly into J2EE containers, light weight containers and any Java application.

Hermes JMS
Hermes is a Swing application that allows you to interact with JMS providers. Hermes will work with any JMS enabled transport making it easy to browse or seach queues and topics, copy (via drag and drop) messages and delete them.

JORAM
JORAM incorporates a 100% pure Java implementation of JMS (Java Message Service API released by Sun Microsystem, Inc.). It provides access to a MOM (Message Oriented Middleware), built on top of the ScalAgent agents based distributed platform. JORAM is an open source software released under the LGPL license.

MantaRay
MantaRay is an innovative open-source data messaging project that was designed to address the continuously changing structure of today's IT environments. MantaRay uses a new approach – peer-to-peer serverless architecture – that allowed its development team to create a solution that is significantly more powerful and more efficient than traditional systems.

OpenJMS
OpenJMS is an open source implementation of Sun Microsystems's Java Message Service API 1.0.2 Specification.

Presumo
Presumo is an implementation of the Java Message Service API. Our goal is to provide an open source Message Oriented Middleware solution based on the JMS API with features not available in other JMS implementations and performance (in terms of message throughput) better, or at least equal to, proprietary solutions. The overall design is a scalable distributed architecture with an emphasis on the Publish/Subscribe messaging paradigm and server-side content based filtering.

Somnifugi
SomnifugiJMS is an implementation of JMS that works inside a single JVM to send JMS Messages between Threads. Somnifugi is particularly useful for isolating the awt Thread so that the user interface will stay lively, for decoupling calls to slower external resources such as database connections, and for speeding up implementations of generic JMS clients by placing decoupled JMS clients in the same JVM.

UberMQ
UberMQ is a clean room implementation of the Java Message Service specification. JMS is a part of the Java 2 Enterprise Edition. We wrote UberMQ because many of the established JMS vendors have turned their back on the core tenets of distributed computing: fast and simple. If you are frustrated with your current JMS vendor, or looking for a solid messaging platform for a new project, please consider our product.