Some notes. The amazon aws ruby gem/ lilbrary used in the amazon examples has a different name to what one might expect (aaws rather than aws) because a different project had already registered a gem with that name in source forge.
to install it (needs write access to the local or remote gem store): gem install ruby-aaws

Here are some links to the Ruby library project documentation http://www.caliban.org/ruby/ruby-aws/ is one of the top pages in the code docs, summarises the library, includes download links and tips on usage.
http://www.caliban.org/ruby/ruby-amazon.shtml is the project's landing page (and mentions the history of how previous versions of the code were deprecated/ rendered obsolete following, "[2008-03-31]...Amazon's decision to shut down access to v3.x of the AWS API. "