Duolingo : I think duolingo can add vocabulary to learn, from my duolingo also increases the smoothness of the english language.
English Central : I think the central english fun but it also we can connect to the teacher outside the country, from central english i started confidentyl speak english and i also enjoy increased although the vocabulary that i use is not so smooth.
Skype : Skype is also beneficial for me because of my skype can connect with friends and can also by people out side the country.