Code-First Membership / Role Provider is built using C# and allows for drop-in type usage / abstraction unlike other code-fist options at the moment.

Custom Membership Provider built with Entity Framework Code-First, for use in ASP.NET MVC and ASP.NET WebForms.

Domain-Driver is a generic framework that enables developers to quickly build rich, expressive domain models. It is both "decoupled from" and "compatible with" any persistence technology. The download includes an example using ADO .NET Entities Framework Code-First persistence.

This is an abstraction layer on NHibernate written in C# language that allow you to easily write NHibernate applications without writing any line of class mapping.