The BBC has a very good website where ELT students can check about their doubts when it comes to understanding grammar issues: Grammar Challenge
Grammar issues appear listed and with just one click you find a page where an ELT specialist gives you a clear explanation on the grammatical point you need to understand, as well as clear written examples. Explanations can be downloaded as mp3 files so that students can listen to them on the go. It is quite suitable for intermediate/advanced students.
There is also a teacher’s section with ideas to get the best of this website in class.