The Managed Extensibility Framework (MEF) is a new, fully supported, dependency injection framework that will be shipping in .NET Framework 4.0. You can find out more over on our CodePlex site:http://www.codeplex.com/MEF.
Enterprise Library is a collection of building blocks from the Microsoft Patterns and Practices Group containing common functionality that developers can consume in their enterprise applications. It also includes a dependency injection Framework (Unity). You can find out more information on their CodePlex site:http://www.codeplex.com/entlib.
Although MEF took ideas and patterns from Unity and Enterprise Library, they are two separate products.
Managed Extensibility Framework Team | My Blog: http://davesbox.com