Extender.js

// Create an inherhit / extend method
Function.prototype.inherits = function (class) {
	$.extend(this.prototype, class.prototype);
}

var ExtendClass = function () {
	// Call the "parent" constructor
	Foobar.apply(this);
	
	// Parent method
	this.foo();
}

// Extended class' method
ExtendClass.prototype.superMethod = function () {
	console.log('cake');

	return this;
}

// Extend the Foobar class with the ExtendClass
ExtendClass.inherits(Foobar);

// Make it global
window.ExtendClass = ExtendClass;

Foobar.js

( function (window, $) {
	/**
	 ** @ Constructor 
	 ** 
	 ** Function constructors should _always_ be capitalized
	 **/
	var Foobar = function () {
		// Properties
		this.foop = 'bar';
	};
	
	/**
	 ** @ Methods
	 **/
	Foobar.prototype = (function () {
		// Private methods
		var privateFoo = function () {
			console.log('private stuff');
		},
		privateBaz = function () {
			return this;
		}
		
		// Public methods
		return {
			foo: function () {
				// Private methods should be called using the apply method
				privateFoo.apply(this);
				
				return this;
			},
			baz: function () {
				return this;
			}
		}
	})();
	
	/**
	 **	@ Static methods
	 **/
	Foobar.staticFoo = function () {
		console.log('static foo');
		
		return this;
	} 
	
	Foobar.staticBaz = function () {
		console.log('static baz');
		
		return this;
	}
	
	
	/**
	 **	@ Static properties
	 **/
	Foobar.defaults = {
		'foo': 'bar',
		'baz': 'foo'
	}
	
	// Make it global
	window.Foobar = Foobar;
	
	
	/**
	 ** @ jQuery plugin
	 **/
	$.fn.foobar = function () {
		return this.each( function () {
			return new Foobar();
		});
	};

})(window, jQuery, undefined);