The name of the site says it all: 5 Minute English will provide you with free, short and quick English learning materials.
Problematic grammatical points involving tenses, conditional sentences, reported speech or tag questions are explained briefly but effectively in simple, everyday language. Example usage is given, followed by exercises to check your understanding.
If your interest is in building vocabulary, you will enjoy the lessons focusing on roots/prefixes and theme-organized vocabulary, all easy to understand and conveniently consolidated by practice questions.
The skills of listening, speaking, reading, writing and pronunciation are dealt with in respective sections. Again, short exercises accompany each lesson to help you test yourself.
A separate area of the site is dedicated to phrasal verbs, idioms and slangs, which I am sure will be of great help to non-native speakers who would like to use the language more naturally.
Among other resources provided by 5 Minute English, you may want to pay attention to the Questions and Answers section, where common English usage problems are discussed, and the Articles section, with some useful guides to learning English.
Site URL: http://www.5minuteenglish.com/