Connexions

Connexions is a dynamic digital educational ecosystem consisting of an educational content repository and a content management system optimized for the delivery of educational content. Connexions is one of the most popular open education sites in the world. Its more than 17,000 learning objects or modules in its repository and over 1000 collections (textbooks, journal articles, etc.) are used by over 2 million people per month. Its content services the educational needs of learners of all ages, in nearly every discipline, from math and science to history and English to psychology and sociology. Connexions delivers content for free over the Internet for schools, educators, students, and parents to access 24/7/365. Materials are easily downloadable to almost any mobile device for use anywhere, anytime. Schools can also order low cost hard copy sets of the materials (textbooks).

http://cnx.org/