Christian Heilmann who is quitting his job as a full-time developer evangelist at Yahoo has made available a demo chapter from a prospective book on YQL.
In case, you haven't heard of YQL, its "a technology that turns the web into a database and allows you to mix and match and filter before writing your first line of code. It also allows you to release an API without any infrastructure, knowledge of authentication and access control. In essence you can use Yahoo’s server infrastructure and processing power to unleash the awesome of the web into your products or the awesome of your data on the web."
Chris has to be one hard-core evangelist because he has published scores of presentations on SlideShare, numerous tutorials & even a handbook on Developer Evangelism
Also see:
Screen scrape with jQuery, AJAX, JSONP & YQL