Check out HOTmaths, a program designed in Australia for teachers, students and parents (to use with their children when doing homework) http://www.hotmaths.com.au/ that works well with all teaching and learning strategies including the Flipped Classroom approach http://en.wikipedia.org/wiki/Flip_teaching.

I find Khan Academy (www.khanacademy.org) particularly useful for teaching (my) kids some basic skills (it goes from basic addition to much more advanced topics), I guess about age 6-16).

Dear Irena and Vitaly

Nice web links and informations, my daughter liked these sites.

Thanks