RESTful Web Services
Imagine that web sites are both human readable and machine readable. Simplicity itself.
In formulating the One Big Database Theory, ReST (Representation, State, Transfer) explains the natural grammar of the Web that makes creating more useful web sites and applications easier and simpler. Imagine if the developer of the engine of the web (HTTP) whispered in your ear that it really is easier--which is what ReST is. Roy T. Fielding laid out an understanding of how the web works.
Note to geeks: Wash SOAP away and forget XML-RPC if you ever knew it. Throw out convoluted API's and embrace sites and services that are intuitive.
Read the book RESTful Web Services, by Leonard Richardson and Sam Ruby. Do not trust anyone doing web technology that has not read this book. http://www.oreilly.com/catalog/9780596529260/