Dropbox - Online Sync and File Sharing
Box - Box offers secure content management and collaboration for individuals, teams and businesses, enabling secure file sharing and access to your files online.
Syncthing - Syncthing replaces proprietary sync and cloud services with something open, trustworthy and...
Google Drive - Access and sync your files anywhere
SpiderOak - SpiderOak makes it possible for you to privately store, sync, share & access your data from everywhere.
Nextcloud - With Nextcloud enterprises host their own secure cloud solution for storage, collaboration & communication from any device, anywhere.