patterns & practices – Enterprise Library

http://www.codeplex.com/entlib

Microsoft patterns & practices

http://msdn2.microsoft.com/en-us/library/ms998572.aspx

MS Enterprise Library

Here are some interesting URL's about best practices, design patterns and the Enterprise Library.

http://msdn2.microsoft.com/en-us/library/aa480453.aspx
http://msdn2.microsoft.com/en-us/practices/bb190359.aspx