Illustrative Mathematics - good source of mathematics tasks aligned to the National Common Core Standards
standards are arranged by:
grade level
then domain
then cluster
Inside Mathematics - good source of mathematics tasks and problems aligned to the National Common Core Standards
standards are arranged by:
grade level
then strand
then choose among:
Problem of the Month: Non-routine problems designed to be used schoolwide to promote a problem-solving theme. Each problem is divided into five levels of difficulty, Level A (primary) through Level E (high school).
Performance Assessment Task: Grade-level formative performance assessment tasks with accompanying scoring rubrics and discussion of student work samples.
Formative Re-Engaging Lesson: Videos of a classroom lesson involving re-engagement around a mathematical concept following a cycle of inquiry, instruction, assessment, analysis, and selection. These lessons include lesson plans, student pages, pre- and post-assessments, and supporting instructional materials.