Extensive Reading Foundation 
Check the ERF site regularly for more information on extensive/graded reading and other ERF projects.

This site is a comprehensive one-stop resource for information on extensive reading, with a special emphasis on its application to Second or Foreign Language Learning.

M-Reader (formerly the Moodle Reader Module) provides online quizzes for many hundreds of graded readers and books for young readers to help learners and teachers track reading progress. 

Extensive Reading Central
A developing site on everything ER.

Japanese ER community promoting ER for language acquisition and enjoyment. Site hosts discussion page, database of readers (including reader ratings), and much more.