Ruby-rabbitmq-client is a project mainly written in Ruby, it's free.
Simple RabbitMQ client for Ruby using JSON-RPC over HTTP as its protocol
A simple client library to access a RabbitMQ messaging server via simple HTTP request instead of using the default RabbitMQ protocol. The benefits are obvious: You don't have to route yet another protocol through firewall but instead rely on the proven HTTP enviroment.
Everything needed to publish basic messages to an exchange is implemented. There's support for receiving messages though it is not yet functional.
You need a running RabbitMQ message broker with the rabbitmq-jsonrpc-channel plugin enabled.