BBC

1. On this site you can find many short videos with some themes. There are a lot of any grammatical videos. You can choose your English level and many others.
2. This resource is so comfortable for use. You can choose specific theme and moreover,  you can use searching and search what you need.
3. If you want to download audio-files, you can do it. 
4. After every video there are short tasks and you can check  how you mastered  new lessons
5. After tests there are answers. 
6. There are tasks for different English level. It depends on your level.
7. I think. the most useful  is that videos affect very important themes and situations. And I can check my knowledge.

 voice of America

1. On this site we can find some different videos, topics, news, audios and a lot of useful information. But, in general, it's American English. And the main part of information is about America.
2. This site rather comfortable for use.There are searching and different sections. 
3. We can download audio. Moreover, there are two formats of downloading.
4. There are videos, but without tasks. Nevertheless, there are subtitles for each video.
5. I didn't find tasks, but you can training new words in Quizlet. There is line on this site.
6. There are tasks for different levels. From low to more advanced. You can choose your level and watch video,and listen audio.
7. As for me, the most important, that there are not only texts, but  audio. It's help me train my listening. So, I learn British English, but, for general development, I have to know American English

skillswise

1. On this site you can find some groups  of information. It's home, reading,writing,spelling and some others.
2. The site is very comfortable for use, because the main information was divided on some groups and it's great. Moreover, there is searching by keywords.
3. We can download tasks after video, but i didn't find how I can download video.
4. There are tasks after each video, topic, text.
5. There are answers for each task and we can download task in two formats. Moreover, we can look tasks online.
6. There are tasks for different levels speakers. Moreover, when you watched video you can choose your level. And tasks are divided on groups.
7. It's useful site.As for me, I found for myself many interesting information. The most important is games. I like games, because with games I better remembering new words and phrases. This site is the best.

CONCLUSION: 

 Finally, I would like to  say several words about these three sites. Each of these sites is interesting and useful. There are sites where we can download lessons, videos,audios. And there is site, where we can download only tasks, but it don't make this site worse than others. To be honest, I so like "skillswise". I don't know why, probably, because there are games and very comfortable interface. I guess, I will use these sites for a long time.

Thank you for attention!