Syncthing - Syncthing replaces proprietary sync and cloud services with something open, trustworthy and...
Dropbox - Online Sync and File Sharing
OwnDrive - OwnDrive is a web-based storage platform allowing the professionals, enterprises, and individuals to easily upload, store, backup, share and collaborate on their files and data with others.
Box - Box offers secure content management and collaboration for individuals, teams and businesses, enabling secure file sharing and access to your files online.
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.