The Code

(function($) {

	var methods = {
		hi : function(who)
		{
			who = who != '' ? "HI " + who + "!": "Who's there?";
			alert(who);
		},
		hello : function(who)
		{
			who = who != '' ? "Hello " + who + "!": "Who's there?";
			alert(who);
		}
	};
	
    $.fn.Say = function(method) {
         // do some checking on method request, if exist call it & pass any arguments to the function
         // else return error
        if (methods[method])
		{
			return methods[method].apply(this, Array.prototype.slice.call(arguments, 1));
		}
		else if (typeof method === 'object' || !method)
		{
			return methods.init.apply(this, arguments);
		}
		else
		{
			$.error('Method ' + method + ' does not exist on jQuery.ipt');
		}
    };
	
})(jQuery);

How to use it

$(document).Say('hi','ahmad');
$(document).Say('hello','ahmad');

Reference: How to create a jQuery plugin with methods?