Check the ERF site regularly for more information on extensive/graded reading and other ERF projects.
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.
A developing site on everything ER.
Start with Simple Stories (SSS) Extensive Reading Study Group
Japanese ER community promoting ER for language acquisition and enjoyment. Site hosts discussion page, database of readers (including reader ratings), and much more.