Final Code

/**
  * Easy Gallery jQuery Plugin
  * Author: Drew Douglass
  * Version: 0.1
  *
  *
  */
(function($){
  	$.fn.easyGallery = function(settings) {

  		//setup some options
  		var opts = $.extend({}, $.fn.easyGallery.defaults,settings);
  		return this.each(function(setting){
  			var options = $.extend({}, opts, $(this).data());
  			$(this).hover(function(){
  				$(this).siblings().stop().animate({
  					opacity: options.opacity
  				},options.duration);
  			}, function(){
  				$(this).siblings().stop().animate({
  					opacity: options.originalOpacity
  				},options.duration);
  			});
  		});

  	}
  	$.fn.easyGallery.defaults = {
  		duration: 500,
  		opacity: 0.5,
  		originalOpacity: 1
  	}
})(jQuery);

Helpful Resources

• A Plugin Development Pattern – Learning jQuery
• Plugin Files/Github Repo

Thank to Jarel Remick for providing the free demo images.