Today's Web is a huge repository of information and everyday an enormous amount of new information gets accumulated into this information base. If we think of a Web site in terms of the popular Model-View-Controller architecture, the information could be found in the Model or in the View. If we consider the View, for the most part the information is stuck inside HTML pages themselves, formatted in some esoteric ways. The Model is a data source that contains the information that is skinned with the View. So, if we can transform a Web site into Web service the internal data can be exposed to the external parties.
If we are to expose the data encapsulated in HTML pages, the best option is to use a technique called Web scraping. Dapper, Teqlo and Yahoo! Pipes are a couple of commonly used scraping technologies.
The data in the Model is exposed mainly via a SOAP/REST API. There are a number of well known REST services like Amazon, Flickr, Twitter, etc that can be consumed using some REST client.
This interesting article by Dimuthu Gamage explains how the WSO2 Web services framework for PHP - WSF/PHP - could be used to consume the Amazon E-Commerce service. The FlickrPal is a Windows shell extension application that is capable of uploading photos to your Flickr account using the Flickr REST API. FlickrPal runs on top of WSO2 WSF/C. And there are a number of decent tools that can post updates to your Twitter account using the Twitter REST API.
