Exploring English: Language and Culture
https://www.futurelearn.com/courses/explore-english-language-culture
Resolva exercícios e atividades acadêmicas
This is a free course, like it says, it´s about exploring the English language and culture.
It is a great course to complement your studies. It is directed at people of minimum pre-intermediate level, but it´s more for intermediate students.
Encontre o professor particular perfeito
After you finished 50% of the course you can get a diploma, the course is free, but the dipoloma is paid. The diploma is only physical, no online version available of the diploma.