We present the perspectives of teachers and others involved in the collaborative design of teaching and learning artifacts across three cases: (a) an independent group participating in lesson study; (b) teachers participating in professional development programs; and (c) a district initiative for producing numeracy tasks. Among the results we found that (a) the role of the facilitator was crucial, (b) different forms of support were present, and (c) the impact extended beyond the involved participants. These cases represent an option for both the design of curricular material for classrooms and a curriculum for teachers' continuous professional development.