There are lots of websites out there, but I thought I’d highlight a few less familiar ones. Although not perfect, the materials I am going to talk about do allow the learner some repetition of already learned concepts. For beginners and learners without much formal education, I believe that online learning is more about reinforcing and maintaining the learners’ existing language skills.
One of my favourite sites that CLB1L to 3L can use independently (once they’ve been shown it a few times) is Games to Learn English. Each game has several different vocabulary themes within each game type. This allows repetition for the student so that they become familiar with how to play each game. Other games on this site are word order games. The games range from quite easy (below) to longer scrambled sentences.