Some useful websites and programms

Multi-skill:

http://www.rosettastone.com/
Rossetta Stone is a programm which allows you to learn different languages starting from any level. But I think it's really useful if you are the beginner, as methods which are used in the programm are  very good for learning simple words and constructions.
Minus: there's no mobile version

For kids (and teachers): http://learnenglishkids.britishcouncil.org/ru -
There're a lot of activities, colourful cartoons, games, exercises and stories, It can help a teacher to make an interesting lesson with different forms of work

Reading and Writing:

http://eslus.com/LESSONS/READING/READ.HTM  - for adults

http://english-easy-ebooks.com/ - adoptive literature

http://www.kidsgen.com/short_stories/ -  for kids

Grammar:

http://www.grammar-quizzes.com/  

There're a lot of rules with simple explanation and nice examples.

For kids

https://www.youtube.com/channel/UC7STes3T0M4F0kuOiExGOtw - nice channel with funny songs. Children  easily remember grammar rules 

Vocabulary:

https://ru.duolingo.com/

https://www.busuu.com/ru/

http://en.leengoo.com/ 

Mobile apps:

Memrise

EasyTen

Busuu

Duolingo

BBC learning English

For kids

Fun English - contains a lot of differens activities, but there're only two free lessons

Lingokids - feature: there are videolessons in the app

Playtime - cool app of British Council