Chapter 3 covered quite a lot it felt like, including the fact that Amazon's S3 is a RESTful service, is quite simple and elegant, and was the main example. This chapter also assumed knowledge of Ruby on Rails when it made analogies between S3 and ActiveRecord, but the main points were clear. I was pleased to see some Python code, even if it was a client talking to a RESTful service written using ActiveResource. Oh, and 'whytheluckystiff' wrote a S3 clone called ParkPlace for hosting your own S3 service!