What are your favorite interactive learning platforms?

Question

SoloLearn is great, I love it but there are many other apps that share similar features but might regard other subjects, what are some other platforms you visit.
For me it's Duolingo and Quizlet which are my favorites. I like the concept of Memrise too but find it a bit hardly adjustable.

Answer 1

For foreign language learning I tried Babbel, Rosetta Stone, Busuu, Beelinguapp and one other app, but I forgot how it was called.
I liked Rosetta Stone best, but it was too expensive. I liked Busuu second to best and the price was reasonable, so I bought a subscription.