Newton Virtual - Learn and enjoy
Brain Games - Boost memory power with free brain games
Eduonix - An e-Library to Learn, Grow and Succeed.
Dualnback.works - Dual N-back is a specific brain training exercise, that's been shown by research - it might improve fluid intelligence.
Crehana - Crehana is an on-demand learning platform.
Pixelogic - Daily Picross - Nonogram logic game with 5000+ puzzles and a daily puzzle