I am pleased to announce that my book Programming Amazon Web Services: S3, EC2, SQS, FPS and SimpleDB is now officially published and should soon be available from booksellers. It will hopefully prove to be a valuable resource for people who are building applications on top of Amazon's infrastructure services, or who are considering doing so.
The book contains a large number of code examples written in Ruby, including example client implementations for all five infrastructure services. This code, as well as corresponding implementations written in Java and Python, will shortly be available for download from the O'Reilly catalog page. There is also a forum where you can discuss the book or ask questions.