"Tahoe-LAFS is a Free and Open decentralized cloud storage system. It distributes your data across multiple servers. Even if some of the servers fail or are taken over by an attacker, the entire file store continues to function correctly, preserving your privacy and security."
RetroShare is a Open Source cross-platform, private and secure decentralised communication platform. It lets you to securely chat and share files with your friends and family, using a web-of-trust to authenticate peers and OpenSSL to encrypt all communication. RetroShare provides filesharing, chat, messages, forums and channels