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Using English: English Language Quizzes
Over 200 short self-quizzes for English learners at beginner and intermediate levels. Quizzes span topics including spelling, grammar, vocabulary, and punctuation.
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Using english.com: English Grammar Quizzes & Worksheets
A nice treasure trove of printable grammar worksheets organized by proficiency level: beginner, intermediate, and advanced. Emphasis is on parts of speech but you'll also find some that focus on common spelling issues and vocabulary...