Wikipedia
TeachersPayTeachers
Teachers Pay Teachers is an open online marketplace where teachers sell their original lesson plans and other course materials to other teachers, and also share for free. By March 2014, the site has attracted over 3,000,000 registered users and 900,000+ original teaching resources, and many teachers are earning significant supplemental income on the site.
TeachersPayTeachers was founded in April 2006 by Paul Edelman, a former NYC Public School teacher, and was acquired by Scholastic Inc. in December of the same year. In March 2009, Edelman repurchased the website and spun it back out as private business.