HotQueue is a Python library that allows you to use Redis as a message queue within your Python programs.

Octobot is a task queue worker for applications that must process message queues with extremely high throughput, minimal latency, and high availability - especially those sensitive to the overhead implicit in receiving and processing many lightweight tasks, such as message delivery systems.

Celery is a task queue/job queue based on distributed message passing. It is focused on real-time operation, but support scheduling as well.

celery is a distributed task queue framework for Django. It is used for executing tasks asynchronously, routed to one or more worker servers, running concurrently using multiprocessing.

ZenQueue is an incredibly simple message queueing system written in Python

High speed message queuing library.

AMQP enables complete interoperability for messaging middleware, both the networking protocol and the semantics of broker services are defined in AMQP.

Ruby interface to Amazon’s Simple Queue Service