On ESL Blues, you will find a huge number of interactive grammar exercises, from "Pre-intermediate to high-intermediate level English".
Note also the diagnostic quizzes and tests.
Would you want to use them with your learners?
I'd suggest that, broadly speaking, we could divide the websites that we might use as language teachers into one of three different categories:
1. Sites for our own professional use
2. Sites that we could use with our learners
3. Sites that we could recommend to our learners
We might also have a fourth category — into which we might dump all those sites that we would not use, because…
ESL Blues I would put into that third category — a site I would recommend to my learners, somewhere where they could get lots of further practice and revision, one which they could use outside class, in their own time.
It isn't, however, one I'd use in class…
We also have grammar, vocabulary and reading exercises on our English courses site.
For any of you struggling to learn Spanish, there are also Spanish grammar exercises.
If you are looking for more exercises, our "Learn Spanish" site again has grammar, vocabulary and reading exercises.