Research suggests the importance of professional development for teachers of at-risk children, and while educational technologies can be harnessed to help support teaching practice in innovative ways, such programs are often limited in scale. "My Teaching Partner (MTP)" was designed to deliver a targeted program of professional development for teaching quality, integrated with early childhood curricula, to large numbers of teachers. It has been used by 235 teachers of at-risk preschool children across the commonwealth of Virginia. MTP links curricula with layers of web-based support, including an on-line consultant--a teaching expert who regularly observes, de-briefs, and extends teachers' educational practice. The research-based curricula support the needs of at-risk Pre-K students in language, literacy, and social relationships; numerous video clips demonstrate effective teaching practice. In this paper, we describe the user-centered design process used and the support services and curricula delivered. The dynamic nature of the website is emphasized, including development practices which enable non-developers to easily contribute and maintain website contents. We discuss the strengths and weaknesses of this approach, and describe the field trial now underway, which includes examination of child outcomes, teaching quality, and teacher reflectivity. Evaluation data from the project are also summarized. (Contains 7 figures and 1 table.)