HUGE LESSON DIRECTORIES

Core Knowledge Units

TeacherLink Free Lesson Plans

Yale New Haven Teachers

Social Studies Free Lesson Plans - Ancient, American, World History

Utah Education Network

BBC Education

Huge Number of Lesson Plans organized by subject (BC)

Smithsonian Lesson Plan Base

Link Collections

Multi-Subject Lesson Plan Site (Ed Sass)

Social Studies Lesson Plans (mrdonn)

Holiday Lesson Plans & Units (mrdonn)

Pro-Teacher

Awesome Library

AtoZ TeacherStuff (lessons, themes, more)