Retroshare establish encrypted connections between you and your friends to create a network of computers, and provides various distributed services on top of it: forums, channels, chat, mail…
VeraCrypt
VeraCrypt is a free open source disk encryption software for Windows, Mac OSX and Linux.
Tor
The Tor software protects you by bouncing your communications around a distributed network of relays run by volunteers all around the world.
OnionShare
OnionShare is an open source tool for securely and anonymously sending and receiving files using Tor onion services.