Many of you know that I have been involved in an advisory role with the Patterns & Practice team for SharePoint. Yesterday the P&P team wrapped up the 2010 guidance for developing apps using SharePoint 2010. If you are a SharePoint developer then at an absolute minimum, you MUST read the documentation that is included in the downloads. The P&P team has some of the best guidance on the various topics covered. Also included in the download is code that will provide some core infrastructure to your SharePoint 2010 projects such as logging and configuration.
Developing Applications for SharePoint 2010 is located at:
http://msdn.microsoft.com/en-us/library/ff770300.aspx