Apache Qpid is a reliable, asynchronous messaging system that supports the AMQP messaging protocol in several common programming languages. Qpid is supported on most common platforms.
On the Java platform, Qpid uses the established Java JMS API.
On the .NET platform, Qpid defines a WCF binding.
For Python, C++, and .NET, Qpid defines its own messaging API, the Qpid Messaging API, which is conceptually similar in each supported language.
Support for this API in Ruby will be added soon (Ruby currently uses an API that is closely tied to the AMQP version).