Microsoft SharePoint 2010 SDK includes documentation & code samples for SharePoint Foundation 2010 and SharePoint Server 2010, which builds upon SF 2010 infrastructure. Documentation includes detailed descriptions of technologies that SS 2010 and SF2010 provide for developers, reference documentation for server & client object models, and step-by-step procedures for using these techs and object models and programming with them. SDK also includes best practices & setup guidance to get started with own custom apps that build & extend upon SF2010 and SS2010 platforms. SDK also includes many code samples that address common customization scenarios and solution building blocks. Future (quarterly) releases will contain additional samples, and you can also check MSDN Code Gallery for SharePoint solutions and code samples.