Load jQuery and Plugins Async: http://www.sharepointjohn.com/javascript-loading-jquery-jquery-plugins-asynchronously/

LoadJS.js

/*
	This function will take the scripts specified and load them in order
	asynchronously.  It will not continue until the specified type from
	each file is loaded.
*/

(function () {	
	function loadScripts () {
		/*
			This loadScript function takes the name of the object as it
			will be assigned to its parent.  For instance, jQuery is the
			name of the object assigned to the window object.  For the 
			plugins, the object name is the name of the jQuery function.
			
			For instance, for a function that runs like $.plugin(), the
			function name to specify is 'plugin'.  
			
			The loadScript will either look for the new object on the 
			window object or in the jQuery functions.  Specify whether
			to look on the 'window' or 'jquery' object.  For the most
			part, only jQuery will be on the 'window' and everything
			else will be 'jquery'
		*/
		loadScript('jQuery', '/jquery-1.7.2.min.js', 'window');		
		loadScript('plugin', '/jquery-plugin.js', 'jquery');
	}
	
	loadScripts();
	
	function loadScript (objectType, scriptUrl, parentObject) {
		var isDef = isDefined (objectType, parentObject);
		if (!isDef) {
			var scriptElement = document.createElement('script');
			scriptElement.type = 'text/javascript';
			scriptElement.src = scriptUrl;
			scriptElement.async = true;			
			document.body.appendChild(scriptElement);
			loadScriptsWait(objectType, parentObject, function () {
				// Write to the console that the JS loaded
				console.log(scriptUrl + ' loaded');
			});
		}
	}
	
	function isDefined (objectType, parentObject) {
		switch (parentObject) {
			case 'window':			
				if (typeof window[objectType] != 'undefined') {
					return true;
				} 
			break;
			case 'jquery':
				if (typeof jQuery.fn[objectType] != 'undefined') {
					return true;
				} 
			break;
		}
		
		return false;
	}
	
	function loadScriptsWait(objectType, parentObject, callback) {
		var isDef = isDefined (objectType, parentObject);
		if (!isDef) {
			setTimeout(function () {
				loadScriptsWait(objectType, parentObject, callback);
			}, 200);
		} else {
			callback && callback();
		}
	}	
})();