Krys got his very popular TechEd Europe session on framework engineering posted.
Framework Engineering: Architecting, Designing, and Developing Reusable Libraries
This session covers the main aspects of reusable library design: API design, architecture, and general framework engineering processes. Well-designed APIs are critical to the success of reusable libraries, but there are other aspects of framework development that are equally important, yet not widely covered in literature. Organizations creating reusable libraries often struggle with the process of managing dependencies, compatibility, and other design processes so critical to the success of modern frameworks. Come to this session and learn about how Microsoft creates its frameworks. The session is based on experiences from the development of the .NET Framework and Silverlight, and will cover processes Microsoft uses in the development of managed frameworks