Rocket Languages has presented itself as useful so far. I would recommend the interactive course for someone who's above the beginner level to avoid struggles and discouragements at first. The speakers really push you forward into speaking, though. However, it gets tricky when you have to use an intermediary language to learn the target one. The possibility of downloading everything in the course has provided a deeper immersion in French once you can carry it around whenever you go. Plus, the audio quality is crystal clear providing a better understanding of how the pronunciation works separately and in context.