I have completely fallen in love with this app. I used to think Babbel was good, but Duolingo is even better and it's completely free. It turns learning a new language into a game, so it doesn't feel like you're learning, then suddenly you realise you're spouting sentences and can remember at least some of the vocab. It doesn't compartmentalise learning, so you don't just study weather, then colours, then adverbs etc. Everything's sort of jumbled together and it challenges you, but in fun chunks. You can log in once a day and do a quick 10-15 minutes speaking, writing and listening.
I'm using the phone app, but it's also available for laptops. I'm trying to focus on learning something that might actually be useful, but my eye keeps roaming to Esperanto, and on the laptop version you can even learn High Valyrian.