Required Reading for SharePoint Developers.  This is a living list; I'll be adding to it as I come across more resources that I think are important enough to share.

General Resources

Books

• Inside SharePoint 2010 (no, not because I was Tech Editor, it's just a very good book)

Magazine Articles

Online Articles

• Writing Better SharePoint Code
• 10 Steps to Better SharePoint Development

Presentations

• Philly .Net Code Camp 

Design Patterns

Books

• Design Patterns: Elements of Reusable Object-Oriented Software - a must read.  Not written for C#, but this is a must anyway. 
• Head First Design Patterns - all of the examples are in Java, but they're easy enough to convert to C# on the fly.  The explanations are generally clear and concise and the style makes this an easy read.

Magazine Articles

Online Articles

• http://wiki.asp.net/page.aspx/276/design-patterns/
• http://www.devx.com/dotnet/Article/33695/1954?pf=true
• http://www.dofactory.com/Patterns/Patterns.aspx - they're selling a product which I haven't looked at yet, but teh examples on their website are quite helpful