Most of the sites on the list are not particularly relevant to ESL, and I’ve already posted about the ones that were.
However, I hadn’t heard of STELLA before. It’s free, and has a pretty extraordinary, engaging, and sophisticated program for people to learn English, Hungarian, Danish. They are completing a program for Spanish.
The problem, though, is the choice of the instruction language (at least for the learning English program) is limited to German, Hungarian, Czech, and Italian.
If your native language is not one of those four, I think the program might be pretty confusing. But if your students do speak one of those languages, I’d definitely suggest you have them check STELLA out.