IPFS!

Syncthing replaces proprietary sync and cloud services with something open, trustworthy and decentralized. Your data is your data alone and you deserve to choose where it is stored, if it is shared with some third party and how it's transmitted over the Internet.

FreeFileSync is a free Open Source software to synchronize files and synchronize folders available for Windows, Linux and Mac OS X. It is designed to be easy to use while having nice visual feedback along the way.

SpiderOak provides an easy, secure and consolidated online backup, storage, access, sharing & sync tool for Windows, Mac OS X, and Linux (Ubuntu, Debian & Fedora). SpiderOak offers a different approach to online backup, synchronization, and sharing. This difference is not just measured in our zero-knowledge privacy policy - the first one ever employed in this setting - but also in our flexible design in handling data from all platforms (Mac, Windows, Linux) and locations (external drives, network volumes, USB keys) in one centralized account. »

Freenet is free software which lets you anonymously share files, browse and publish "freesites" (web sites accessible only through Freenet) and chat on forums, without fear of censorship. Freenet is decentralised to make it less vulnerable to attack, and if used in "darknet" mode, where users only connect to their friends, is very difficult to detect.

SugarSync lets you synchronize, backup and remotely access files and folders across your PC or Mac. You can also remotely view files from Windows Mobile, Blackberry, iPhone, Symbian and Android.

Librevault is an open-source peer-to-peer file synchronization program, designed with convenience and privacy in mind. Our goal is to make a better alternative to BitTorrent Sync and Syncthing.

SyncTrayzor is a wrapper for Syncthing which allows Syncthing's window to be hidden in the tray area. SyncTrayzor has a built-in web browser to manage Syncthing without opening your browser. SyncTrayzor can be configured to automatically start at PC startup. A portable version is also available.

Pydio is the mature alternative to Dropbox and Box.com, to build your own box, on your own servers.

SparkleShare is a Free Open Source syncing tool. Its light, secure and easy to use. SparkleShare allows you to setup your own servers so you always keep control on your data.

Syncany is an open-source cloud storage and filesharing application. It allows users to backup and share certain folders of their workstations using any kind of storage, e.g. FTP, Amazon S3 or Google Storage.

Minimalist Drag & drop file sharing JS applicationDrag, drop and share