个人做的摘记了，懒得翻译，大家自己看吧。

Razor （一个集成的新的View Engine，使代码简洁了不少。）

JavaScript Improvements

Improved Validation

Output Caching

除了支持在url 或 action-method级别的支持外，新增对页面部分(partial page)的output支持（类似于以前的

asp:Substitution控制的功能）

Previous releases of ASP.NET MVC supported output caching content at a URL or action-method level

With ASP.NET MVC V3 we are also enabling support for partial page output caching

Better Dependency Injection

 You can instead just register a Dependency Injection framework with ASP.NET MVC 3

之前是需要自己去定一个类来做这个DI工作，现在只需要简单注册下类就好了。

以下是更多的新功能：

ASP.NET MVC 3 includes dozens of other nice improvements that help to both reduce the amount of code you write, and make the code you do write cleaner.  Here are just a few examples:

• Improved New Project dialog that makes it easy to start new ASP.NET MVC 3 projects from templates.
• Improved Add->View Scaffolding support that enables the generation of even cleaner view templates.
• New ViewBag property that uses .NET 4’s dynamic support to make it easy to pass late-bound data from Controllers to Views.
• Global Filters support that allows specifying cross-cutting filter attributes (like [HandleError]) across all Controllers within an app.
• New [AllowHtml] attribute that allows for more granular request validation when binding form posted data to models.
• Sessionless controller support that allows fine grained control over whether SessionState is enabled on a Controller.
• New ActionResult types like HttpNotFoundResult and RedirectPermanent for common HTTP scenarios.
• New Html.Raw() helper to indicate that output should not be HTML encoded.
• New Crypto helpers for salting and hashing passwords.
• And much, much more…

原文来自：http://weblogs.asp.net/scottgu/archive/2011/01/13/announcing-release-of-asp-net-mvc-3-iis-express-sql-ce-4-web-farm-framework-orchard-webmatrix.aspx#7692548