Tanzim Saqib wrote a very nice article on how to create controls in Volta. His article gives step by step instructions on how to write a Flickr control that you can reuse  in your pages. The control covers the Flickr API, how to make asynchronous requests to Flickr’s REST APIs, parsing the resulting xml, dynamic building of UI and including resources (css).  The same basic principles can be applied to building widgets for any number of different services.