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.

Tornado is an open source version of the scalable, non-blocking web server and and tools that power FriendFeed.

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.

Distributed in-memory application cache platform. Like memcached for Windows.

Scalr is a fully redundant, self-curing and self-scaling hosting environment utilizing Amazon's EC2.

Elastic computing.

SQLscaler simulates production workloads in a test environment and providing in-depth analysis of test results so you can spot problems before going into production.