In short: Some great materials. The best parts are the stories. You can read, listen, and read simple versions. They are written by Kieran McGovern and he is very talented. You can learn more about him here.
Though the site design has improved recently, there are still broken links. Sometimes, the site is confusing. Most links open in a new window, so if you browse the site, you need to close a lot of windows.
For students: Check out the podcasts page for an excellent collection of listening materials.
For teachers: Click on the “reading” tab on eslreading.org to learn all about choosing ESL books (readers) for your classes. You can also read an article about writing readers.