I use frantastique, as it appeals to me more than other online courses because of the story lines, and you get snippets of french culture along with it (music, film etc). Duolingo’s beeps irritated me in the end and I had outgrown it anyway. The fact that I have to pay for frantastique makes me do it every day!
If you want to do a free trial please use this link, as if you then go on to sign up I get a free month!
I did also do a formal french qualification, the DELF, just because I’m geared to formal education. And it was useful, but not as useful as talking to people!