I've started many times Chinese language classes, but only ThatsMandarin is able to really teach me Chinese. They don't follow the standard HSK books, but have their own materials online. Video's, texts, listening exercises, reading exercises, writing exercises. The videos are the best ones. You can chose to listen only, or add pinyin subtitles, or add English subtitles. In the texts you just click a character (or combination of characters) and get the meaning explained. Super way of learning the language.
And a big "thank you" to my teacher. The 50 minutes class are over before I notice.
(I follow online 1-on-1 class)