The Yahoo! Web Developer Network provides a one page overview of JSON, giving a quick tutorial on JSON, how to get Yahoo! Web services to emit JSON, offering an output of a JSON object literal as well as using a callback function method. Yahoo! also describes how their web services typically translate their XML structures into JSON.
Tim Huegdon and Mark Aidan Thomas create an elegant wrapper to the YUI Connection Manager that manages repeating Ajax JSON requests. Tim describes the use of Custom Events, and the use of the Observer design pattern, dissects the code and offers a tidy demonstration of the working code. This simplifies JSON requests into declaring a simple function to process the returned JSON object, and a single line to fire off the request (within a setInterval if required)
Three top features of jQuery: the multitude of selectors, manipulating attributes, and tacking Ajax/JSON requests. Choses jQuery over Prototype
PPK describes the three main data formats for requesting data from the server, weighing up the advantages and disadvantages. In the ensuing discussion the general feeling is that JSON is the most popular and simplest method.