Run by Jennifer Frost , the English Grammar website is a superb and free English language resource, aimed at students but equally handy for teachers. The site offers a huge range of grammar explanations and downloadable lessons, categorised by grammar topic.
The site has materials for students of all levels, so it is useful both for native speakers and also students of English as a second language, though as the site is written entirely in English, it is probably best suited to ESL students who have already reached an intermediate level.
Navigation is clear and easy. On the left-hand side of the page is a column entitled “Topics” from which can choose your topic of interest. There’s also a handy search box if you’re in a hurry.