SaluSafe is an encrypted email, chat, and file storage and sharing system. Your email and files are highly encrypted end-to-end, and cannot be intercepted by any third party. It was built from the ground up for security via strong cryptography, and is not just another security wrapper on top of an existing email solution.
PerlShare is a DropBox drop-in to create your own private file sharing "cloud". It consists of two parts; a client and a server. The server part lets you configure a Linux machine to accept PerlShare clients. PerlShare behaves a lot like DropBox. On collisions, for example, it creates conflicted copies. The workhorse for synchronization is Unison, a very reliable piece of software from Pascal Bach.
PeerProject is a versatile peer-to-peer filesharing client and file manager. It's intuitive and aesthetic while supporting many networks and features, including BitTorrent, G2, Gnutella, eDonkey, DC++, IRC, HTTP/FTP, and more. It's a mainstream fork of Shareaza p2p, for Windows and WINE.
Coquelicot is a “one-click” file sharing Web application with a focus on protecting users’ privacy. Its basic principle is that users can upload a file to the server, and in return they get a unique URL which can be shared with others in order to download the file. Coquelicot aims to protect, to some extent, users and system administrators from disclosure of the files exchanged from passive and not-so-active attackers.
Datum is a Web application which shares data from databases and information related to these databases. The core of the software provides user management and permissions, news, file sharing, visualisation of the database schema through WWWSQLDesigner, data reports with charts, dynamic charts, an asynchronous daemon, internationalization, a help system, database management with optimization and triggers, and user history. Modules can be added to add special functionalities or interfaces for a database.