Here are some websites where you can study for free!

Isn't it great!?

Here they are:

http://study.com

http://www.openculture.com

Apart from them there are also websites already shared with you:

https://www.edx.org  and https://www.coursera.org

Differences between Portuguese and English

http://www.sk.com.br/sk-idiom.html

Here is a great website to learn some English differences:

http://www.dailywritingtips.com