Reading is one of the four main skills when it comes to learning a language (the others being Listening, Speaking, and Writing). You can develop your reading skills by reading the online press, or free e-books, but I've dealt with those elsewhere in this guide. Here, I am going to list some reading resources which are specifically aimed at learners of English.
5-minute English Reading Lessons — Short texts with vocabulary and true/false quizzes.
Daily ESL — Listen and read along to short texts on everyday topics.
DailyLit —Read literary classics and great new fiction in short installments delivered by email.
Dreamreader.net — Graduated reading materials suited to different levels of English ability.
EnglishClub Reading — Reading practice materials, including short stories, for ESL learners.
ESL Lounge — Reading exercises at four levels.
ESL Reading Worksheets — Each PDF worksheet includes a short reading paragraph, and a true-false exercise. Suitable for lower levels.
eslreadinglessons.com — Read texts online and then answer questions about what you have read.
LearnEnglish Teens Reading Skills Practice — Activities at different levels from the British Council.
Linguapress — Intermediate level English reading resources. See here for advanced resources.
My English Pages — Short texts with true/false comprehension questions.
Read Listen Learn — Short stories adapted from works by over 50 authors, articles on history, science, crime, sport and more. Graded at 5 different levels. With audio - listen while you read.
Readlang — Browser extension that translates words & phrases live on any web page, or upload your own texts. Read my review here. Watch demo video here.
Stories and Poems (British Council) — PDF texts with reading activities. Some stories also have audio.
TeaTime Mag — Articles especially written for learners at three levels. With audio.
Guide to Reading for English Learners — Tips and strategies to become a stronger reader.
How to Effectively Improve Your English Reading Skills on Your Own — FluentU.
Improve Your Reading Skills with 8 Easy Steps — FluentU.
10 Great and Easy English Books You Must Read — FluentU.
9 Great Novels to Help Improve Your English — Pearson English Blog.
9 Classic Novels for Students of English as a Foreign Language — Oxford Royale Academy.