Syncthing - Syncthing replaces proprietary sync and cloud services with something open, trustworthy and...
WeTransfer - WeTransfer is a free service to send big or small files from A to B.
Dropbox - Online Sync and File Sharing
Microsoft OneDrive - Secure access, sharing & file storage
Hightail - The professional way to send & share files and folders with anyone
Google Drive - Access and sync your files anywhere