Mega - Secure File Storage and collaboration
Dropbox - Online Sync and File Sharing
Google Drive - Access and sync your files anywhere
Syncthing - Syncthing replaces proprietary sync and cloud services with something open, trustworthy and...
ownCloud - ownCloud is an open source project enabling businesses to host their own cloud storage while maintaining regulatory and compliance needs.
Freehold - An open, secure, and lightweight platform for your files and data.