I've just found out about this great website, the KISS Grammar site. In my humble opinion, it could be a great resource for ELLs, even though it seems to aim toward native English-speaking children in America.
But before hasting to add that to ELL's resource page, I would like to hear your opinions first. (I'm not sure about its correctness, but from what I read in American teacher discussion threads, it seems to be a great resource for their classes.)