David Dorward compares dot notation and square bracket notation, where square bracket notation can be used where dot notation can't. Recommends using dot notation, because its easier to read, and square bracket notation when it can't be done with dot notation.
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.