1.Bundling and minifications 2.Web API 3.Mobile Application support and mobile application template.
http://www.asp.net/mvc/tutorials/hands-on-labs/whats-new-in-aspnet-mvc-4
1-Chart, WebGrid, Crypto,WebImage, WebMail Controls All these are available in MVC3 and in MVC4. 2-TempData, ViewData ,ViewBag are available in MVC4. 3-MVC4 provides better support for Jquery like Jquery Mobile.
1. Display Model. 2. Web API. 3. Mobile Application Template. 4.Using Asynchronous Controllers etchttp://www.asp.net/mvc/tutorials/hands-on-labs/whats-new-in-aspnet-mvc-4