RetroShare is a open source cross-platform, private and secure decentralized communication system. It lets you to securely chat, share photos, videos, and more, using 
OpenPGP to authenticate peers and 
OpenSSL to encrypt all communication.
RetroShare features:
Chat
Send text and images. Discuss with various people in chat rooms. Express your emotions with the rich smiley set. Use distant chat to securely chat with friends-of-friends. More Info »
Voice and Video
Make free and secure calls with the VoIP plugin. Catch up face to face with a video call.
Mail
Send encrypted messages to other members of the network. Retroshare can store encrypted messages on friends nodes to deliver messages while you're offline.
File sharing
Share files with your friends or with the whole network. Use the search to find files. Retroshare uses swarming similar to BitTorrent, to accelerate the download. This makes it possible to share big files with 1GB or more. Your privacy is protected with anonymous tunnels. Only your direct friends might learn which files you download.
Forums
You can read and write forum posts offline. This is perfect while you're on the go. When you have an Internet connection, Retroshare will automatically sync forums with your friends. Decentralized forums are censorship resistant by design.
Posted
Share your favorite links. See which links others like. Vote and discuss links.
Channels
Publish files in channels. Subscribe to channels and automatically download the latest files. Comment on files and spread them to your friends.
