BBC Learning English has been teaching English to global audiences since 1943, offering free audio, video and text materials to learners around the world.
The website provides free English test to help adult learners to find their English level. There are various sections to support users' different learning needs, including grammar and vocabulary.
IdiomsTube is a computer tool developed by Dr Phoebe Lin of the Department of English, The Hong Kong Polytechnic University. The tool helps users to learn English idioms from watching any subtitled YouTube videos.
The Prudue OWL offers free resources including Writing and Teaching Writing, Research, Grammar and Mechanics, Style Guides, ESL (English as a Second Language), and Job Search and Professional Writing.