Designing a Secure REST (Web) API the Amazon Way without OAuth

I have been finding an easy to understand and implement way to secure an API service. I know OAuth is kind of the standard but there isn't a easy to understand article explain the details of how it works and I could make use of it. Then I read there is OAuth 2 coming out, despite Facebook Graph API and GitHub is using it. The standard is still on draft and there isn't much blog post that talk about it in details. Then I came across this article, which use easy to understand english to provide a method to secure an API service the Amazon way (BTW, the article also claimed Amazon has the most API traffic in the world now). It is really an easy to understand read. Despite the author say about OAuth2 is on the way. I will still stick with this implementation for the time being.

Designing a Secure REST (Web) API without OAuth