English Grammar Guide
This site from Education First (EF) has a collection of free English learning resources designed to help study conversational English. Provides links to grammar exercises, usage, vocabulary, idioms, and quotes.
English Grammar Exercises
Grammar lessons and exercises on voice, tense, articles, and spelling are available for free.
English Grammar Secrets
English grammar lessons with clear explanations, quizzes, and fun exercises.
ETS- Free English Grammar Exercises and Tests Online
Contains basic grammar exercises and tests, English tenses exercises and tests, advanced grammar exercises and tests, and exercises and tests relating to commonly confused English words.
Contains free English Grammar exercises on conjunctions, prepositions, agreement of verb with the subject, case, punctuation, dangling modifier, and more.
Oxford Practice Grammar Online
Offers practice exercises and tests in Basic, Intermediate, and Advanced levels.
Perfect English Grammar
Contains exercises on various verb forms, voice, clauses, prepositions, adjectives, gerunds and infinitives, and linking words.