Sites that has proven useful to me

The MVC framework site
The Model-View-Controller (MVC) architectural pattern separates an application into three main components: the model, the view, and the controller.

The blog of Scott Guthrie

Code Project
Source code and tutorials for software developers and Architects.

NHibernate Forge
NHibernate is a mature, open source object-relational mapper for the .NET framework.

Autofac is an addictive Inversion of Control container for .NET 4.5, Silverlight 5, Windows Store apps, and Windows Phone 8 apps.

Stack Overflow
Stack Overflow is a question and answer site for professional and enthusiast programmers.

Scott Hanselman

An introduction - CQRS stands for Command Query Responsibility Segregation and is a model for highly scaleable sites. - by Martin Fowler - by Microsoft Patterns & Practices

C# Language Specification
The C# Language Specification is the definitive source for C# syntax and usage.

The official ASP.NET website.