Yesterday the Amazon Simple Queue Service moved from beta to production. SQS provides persistent messaging with the scalability and reliability of Amazon’s infrastructure. As a developer you can create an unlimited number of Queues and store unlimited messages in a Queue. As usual we manage your data in highly reliable fashion, capable of surviving complete data center failures.
The API is dead simple: Create, Send, Receive and Delete. With sufficient access control such that you can determine who can read and write your queues. We have chosen a concurrency model where the process working on a message automatically acquires a leased lock on that message; if the message is not deleted before the lease expires it becomes available for processing again. Makes failure handling very simple.
Charging is as inexpensive as S3: 10 cents for a 1000 messages, and 20 cents per Gigabyte of data transferred
Code Samples and Documentation can be found here.