Syncthing allows you to share all of your data between multiple devices without having to worry about your security being compromised by cloud services.

Tag your files and emails, add comments and share your tagging with your colleagues. Tabbles is a relational file manager, that allows you to organize and search your files in a new way. It works

Volafile.org provides free temporary online storage, convenient for sharing files between colleagues and friends.

Zoho Docs is an online file management tool that lets you store files securely, share them with friends, and sync them across all your devices.