English as a 
Second Language (ESL) is an umbrella term used to define those for whom English is not their native language. For some, the term ESL may be a misnomer, as it may be used to designate those for whom English is in actuality their third, fourth, or fifth language, not necessarily their second. For this reason, there are now several terms used in addition to ESL.
The American Way of Writing by 
Better Sentence Writing in 30 Minutes a Day by 
Essentials of English Grammar by 
Improve Your Writing Book by 
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.
The exercises in this category cover a wide range of topics, but have been designed for second language writers of a variety of proficiency levels.
Practice your English with free interactive listening lessons, reading exercises, quizzes and games.
USA Learns has four English courses to help you learn beginning and intermediate English. The courses include videos and interactive learning activities to help you practice and improve your English skills in listening comprehension, vocabulary, grammar, spelling, pronunciation, reading, writing, speaking and life skills.
Includes a list of websites will help you continue your English education online.