Duolingo
Brainly
Livemocha
Tagged (website)
Odnoklassniki
hi5
Xanga
Netlog
Badoo
FriendFeed
Twoo.com
Friendster
Ask.fm
Viadeo
Koo (social network)
Language learning platform
busuu.com
Busuu is a language learning platform on web, iOS and Android that allows users to interact with native speakers. In 2021, Chegg acquired Busuu for $436 million. Wikipedia