"The challenge for environments supporting self-directed learning is to allow learners to work on authentic problems and tasks of their own choosing, and yet still provide them with learning support contextualized to their chosen problem. Although repositories of objects are an important resource for designers creating artifacts within a certain domain, economies of educational knowledge, not just of objects, must address the self-directed learning needs of the community that the economy is meant to support. These challenges, some of our approaches to them, and their illustrations in the context of educational economies of knowledge form the core of this article."