ASP.NET MVC 3 is a framework for developing highly testable and maintainable Web applications by leveraging the Model-View-Controller (MVC) pattern.
Some important features of this release as given in the overview notes are
- The Razor View Engine
- Support for Multiple View Engines
- Controller Improvements
- Model Validation Improvements
- Dependency Injection Improvements
- Other New Features
Here are some important links:
You can also check plenty of ASP.NET MVC 3 Tutorials over here
Oh I love the Microsoft Web stack, as it gets better with every release!