This is the U.S. State Department's website to support their overseas English instructors. There are both classroom and professional learning materials for all areas of ELA here.

This website offers "tons" of printable worksheets for teachers with grammar exercises, phrasal verbs, games, and more. 

LiveWorksheets is a website filled with various lessons from teachers. Each lesson is designed to give students the ability to edit and submit worksheets directly on the page without needing to download. 

Ereading is a website with worksheets to help build writing skills and improve comprehension skills. Teachers can download PDFs or HTMLs of assignments. 

SoftSchools covers a variety of subjects and materials. Teachers can find writing activities, comprehension assignments, and games to help improve writing and reading skills. 

Quizzes, tests, exercises and puzzles to help you learn English as a Second Language (ESL). This project of The Internet TESL Journal (iteslj.org) has thousands of contributions by many teachers.