I've gotten heavily into the JSON (JavaScript Object Notation) data format because it is more convenient than XML for client-side AJAX web applications. I have had to remove many of the sample pages in my AJAX portfolio because everyone keeps changing their API. This is making web applications very fragile. On the positive side, this could potentially create more work for me fixing broken AJAX calls.
One of my few remaining clients often gives me a project involving a web service or REST API which he wants to use. I've worked with some FedEx web services and the Bing Maps REST Service for him.
If you are a web developer, you can view the page source to find the JavaScript source code. I am using a few JavaScript libraries like jQuery.
NOTE: I'm not responsible for some of the content that may show up from these third-party web sites.