Just came across some beautiful videos on Office 2010 Development and would like to share with you.
Introducing Office 2010 – whats new in Office 2010 and its integration with SharePoint
Office 2010 Development Tools – various tools that supports development of office customization and the enhancements in them
Developing Office 2010 Customizations – customizing UI in Office 2010, concepts needed for Office 2010 development on both the server and client
Introduction to Office 2010 Developer Roadmap Module – a brief description of this module
Another noteworthy thing is Development Lab. Go through the link for more details.