YUIDoc is one of the best solutions to easily generate documentation for your projects JavaScript.
The syntax is nice and clear and allows easily documenting your JavaScript files.
Here is a small example to document a method of a JavaScript class (code taken from the YUIDoc website).
/**
* My method description. Like other pieces of your comment blocks,
* this can span multiple lines.
*
* @method methodName
* @param {String} foo Argument 1
* @param {Object} config A config object
* @param {String} config.name The name on the config object
* @param {Function} config.callback A callback function on the config object
* @param {Boolean} [extra=false ...
