Bildungsmediathek NRW: On this page you find explanations and rules of the English grammar. They are divided into four levels. At the end of each explanation site there's a link to the exercises where you can practise and check your knowledge.

CONTAKE: Online Übungsseite zu den verschiedenen Zukunftsformen - vorher eine Seite zum Studieren und Einprägen, dann 6 Onlineübungen; going to, future progressive, future tense, will future

Hessischer Bildungsserver: Explanations and interactive exercises for a variety of future tenses: Simple Future Tensegoing-to futurePresent Progressive in the futurePresent Simple in the future