swap-bot - Swap-bot is a online service that organizes group swaps and a community of creative individuals.
PenPal World - Connect with people all over the world
Postcrossing - A postcard exchange project that invites everyone to send and receive postcards from random places in the world. For free!
Unbordered - Unbordered app comes up with features to help you in finding the perfect language practice and exchange partners so you can practice foreign languages right through your mobile phone.
InterPals - InterPals is a friendly community of over 5 million friends, language learners, travelers and penpals.
We3 - AI that finds you the most compatible people nearby