Up-to-date guidelines and tutorials on style and referencing.
This site provides wonderful explanations and exercises related to grammar, vocabulary, word order, types of speech as well as various English tests and an online English dictionary.
NIU Online Tutorial on Effective Writing Practices: http://www.niu.edu/writing tutorial/punctuation/punctuation01.html
Covers grammar, punctuation, various ways in which papers are written as well as strategies for clear and effective writing styles. Not only does this site review these concepts and provide examples for clarification, it also offers quizzes so you can check your understanding of these topics.
Purdue OWL Exercises & Explanations
Related Exercises: https://owl.english.purdue.edu/exercises/
The first link provide instructions on various aspects of writing, including grammar, punctuation, forms of writing (academic, correspondence, applications, etc.)
Towson OWS: webapps.towson.edu/ows/index.asp
Excellent site that offers diagrams which help you to see the parts of speech you are focusing on. Not only do you get a lot of examples, but it also provides self-teaching units with exercises and answers. Topics covered by the site includes: parts of speech, sentence structure, punctuation, capitalization, abbreviations, proper use of phrases, commonly confused words and information on plagiarism.
Periods vs. commas: http://www.grammarbook.com/punctuation/commas.asp
Gives good examples of when to use each.
Has a lot of examples and quizzes (though you have to drill down for them).
Has really helpful and clear diagrams highlighting the important things to consider when you are writing sentences. Also has links to exercises which allow you to practice what you are learning and which will grade them once you are finished.
Activities for ESL Students: http://a4esl.org/
Allows you to practice/test your grammar and vocabulary. Some quizzes are bi-lingual, so you can practice translating from your language into English and vice versa.
English Club: https://www.englishclub.com/grammar/
Offers explanations and examples of various parts of speech as well as grammar quizzes.
Offers tutorials on various parts of speech as well as practice exercises.
Wyzant Resources: https://wyzant.com/resources/lessons/english/esl/activities_and_quizzes/activities/conversation
This site offers great explanations of various parts of speech and how they function. Unfortunately, it does not provide a chance to practice what you just learned, but you have many other options on this list which allow you to test your knowledge.
Dave's ESL Café: http://www.eslcafe.com/students
This site will not help with your academic language, but will help you master English idioms and slang. It also helps explain various phrasal verbs and offers quizzes on a variety of topics.
Randall's Self-Study Guide: http://www.esl-lab.com/
This site provides a TON of listing exercises and quizzes to help you improve your listing skills. It even offers a section of listing exercises for academic purposes! It also provides 20-minute ESL vocab lessons.
Not only does it offer practice TOEFL, IELTS, TOEIC and FCE tests, it also gives you opportunities to practice/test your understanding of grammar, pronunciation and vocabulary.
Allows you to practice the listening, reading and structure components of the TOEFL test.
Test Prep Review: https://www.testprepreview.com/toefl_practice.htm
The site allows you to practice for a TON of different tests (ACT, MCAT, SAT, TOEFL, Professional exams, etc.). This link is for the TOEFL page, where you will find study guides, flashcards and practice questions.
Exam English: http://www.examenglish.com/
This site offers practice test for a variety of English tests. It also offers lists of topics and exercises to help you with grammar and vocabulary you need for these tests. One thing that might especially helpful is the list of academic vocabulary (sorted by topic), which might help you write more clearly!
Graduates Hotline: http://www.graduateshotline.com/sampletoefl.html#.WASOhPl95D8
This site just offers a number of TOEFL practice tests.