Postcrossing - A postcard exchange project that invites everyone to send and receive postcards from random places in the world. For free!
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
swap-bot - Swap-bot is a online service that organizes group swaps and a community of creative individuals.
TechEvents.co - Tech and startup events aggregator
Random PenPals - Get a quarantine PenPal in 10 seconds
Facebook Local - Discover places to go and events happening near you