Updated: SharePoint 2010 SDK–Aug 2010
The SharePoint SDK has been updated. You can view the new SDK contents online at http://msdn.microsoft.com/en-us/library/ee557253.aspx or you can download the SDK for offline viewing from http://www.microsoft.com/downloads/en/details.aspx?displaylang=en&FamilyID=f0c9daf3-4c54-45ed-9bde-7b4d83a8f26f. The updated SDK contains new documentation, code samples and intellisense files.
Here is a complete list of code samples in the SDK : http://code.msdn.microsoft.com/sp2010sdktwo
These 2 articles outline the changes that are in the updated SDK: