Box - Box offers secure content management and collaboration for individuals, teams and businesses, enabling secure file sharing and access to your files online.
Dropbox - Online Sync and File Sharing
Microsoft OneDrive - Secure access, sharing & file storage
Microsoft OneDrive for Business - First of all, we think it appropriate to make it clear for the readers, Microsoft OneDrive for Business is different from what is Microsoft OneDrive that is only a cloud storage and limited sharing service.
Google Drive - Access and sync your files anywhere
ownCloud - ownCloud is an open source project enabling businesses to host their own cloud storage while maintaining regulatory and compliance needs.