Postcrossing - A postcard exchange project that invites everyone to send and receive postcards from random places in the world. For free!
Kibii - Discover exciting things to do!
swap-bot - Swap-bot is a online service that organizes group swaps and a community of creative individuals.
EventsBase - Find the best professional events nearby or globally
Random PenPals - Get a quarantine PenPal in 10 seconds
Triip.me - The happiest way to travel in 227 countries