チュウ太の読解教材バンク (Reading Comprehension Teaching Materials Bank)
This site from Reading Tutor has reading material in Japanese and you can choose the difficulty level from 1 star easy to 5 stars difficult. The writing is supplemented by a dictionary of the word that you click on and the word is also added to your list at the bottom. Just check it out to get the picture.
Sources: “Kawamura”, “Kitamura & Hobara” | Subject: Reading Material