I could have sworn we had a CW meta post that listed references useful to English learners; dictionaries, sites like lang-8, grammar references, etc. Since resource requests are off topic, this post was useful to link as a reference when such questions were asked on the main site.
I tried to find it today, though, and was unsuccessful. (I think this happened to be once before as well.) So, does anyone out there with better search capabilities than me know where I can find it? Alternatively, if I'm wrong and there never was any such post (I know for sure we talked about one) then we should create it. So let's start building up some resources as answers to this question, and we can move all of them into a CW post later on if the old one isn't found.