OpenAMQ is a fast, stable, free implementation of the AMQP (www.amqp.org) messaging protocol. It gives applications high-performance messaging (delivery of opaque data) across loosely connected networks. It is capable of handling up to 600k messages per second depending on the hardware, with a latency around 300 microseconds. It is multithreaded and supports C/C++ and Java on Linux, AIX, Solaris, OS/X, Windows, and OpenVMS.
Blue Mind is a messaging and collaboration platform. It offers scalable shared messaging, calendars and contacts with advanced mobility (iPhone, iPad, Android, etc.), and Outlook and Thunderbird connectivity support. Designed with simplicity as a goal, it uses Web 2.0 technologies with a Javascrit UI, offline Web capability, and a Web-services-oriented pluggable architecture.