Helpful Resources

To develop your vocabulary skill:

COCA Corpus: It is a free tool for the first ten uses, and then it requires a registration. It is very helpful in searching for any English vocabulary to see its form, pattern, authentic uses, various contexts, POS, accompanied prepositions, collocations... 

Thesaururs.com: This is a free reference work that lists words grouped together according to authentic similarity of meaning, containing synonyms, antonyms, usages, related words, creature, earthling, verbs make ready with supplies, grown-up, and individual. 

To develop your grammar skill:

Grammar for learners of English: This is a great learning tool for public, ESL students, and anyone needing to refresh English grammar skills. It gives the opportunity of practicing language rules by hundreds of quizzes cover parts of speech, parts of the sentence, mechanics of grammar.

ESL Games World: This Website provides lots of interactive and funny exercises for ESL students. It is free of charge.