Find some great ideas here on building vocabulary, which can be done at home or in school
Strategies for introducing new vocabulary into the classroom or at home
British Council Learn English - Sections for kids, teens and adults to help you develop and improve all your English skills
BBC learning English - a fantastic resource with courses for language learning. Aimed at older teens and adults. The Grammar Gameshow is a particularly engaging way to learn and review grammar. (CEFR B1 upwards)
Cambridge online dictionary - includes an EAL learner's dictionary as well as many bilingual dictionaries. An excellent resource for a language learner.
Oxford online learner's dictionary - another excellent online dictionary. Find simple definitions of words AND how to use them in a sentence.
Linguascope - This is for lower level students
Song Lyrics - This is a great website to practice your English listening skills by completing listening activities all linked to your favourite English language pop/rock songs.
Write and Improve - This website allows you to complete writing tasks, before checking it for you and finding your errors.
Cambridge English - This site allows you to practice all your English skills in one place.
Interactive Worksheets - Complete worksheets online covering many different grammar points and the site will mark them immediately for you.