Interestingly enough, Page and I have both started to look into Design Patterns and using proven best practices.  Microsoft has been posting lots of articles on this recently, several of which are outstanding:

It is one thing to know how to seperate your presentation, business, and data layers.  It is another thing to know how to do it right.

Design Pattern Favorites

Designing Data Tier Components and Passing Data Through Tiers
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnbda/html/BOAGag.asp

You can never take testing too seriously.  And it is one of the more often overlooked parts of a project.

Testing Software Patterns
http://msdn.microsoft.com/architecture/patterns/testingpatterns/default.aspx

Design Pattern Portals

.NET Architecture Center Home
http://msdn.microsoft.com/architecture/

Microsoft patterns & practices
http://www.microsoft.com/resources/practices/

A little of everything:

http://asusrl.eas.asu.edu/papers/Design-Pattern-Testing.htm

http://www.enteract.com/~bradapp/docs/patterns-intro.html

http://www.jguru.com/faq/Patterns

http://www.hillside.net/

http://patterndigest.com/

http://hillside.net/patterns

http://www.cs.wustl.edu/~schmidt/patterns.html

http://www.martinfowler.com/eaaCatalog/