Dropbox will enable you to store your files instantly and optionally share them in Windows, Linux, and Android.

Microsoft OneDrive is a cloud-based service that creates a folder that automatically backs up everything between your computers and OneDrive.com.

Google Drive is a cloud file storage and synchronization service encompassing Google Docs, Sheets, and Slides. Google Drive permits the collaborative editing of documents, spreadsheets, presentations, drawings, forms, and more. Try the Save to Google Drive Chrome extension.

MEGA is a functional cloud backup extension that provides solid security and privacy features.

With SugarSync, you decide which folders you want to sync and where you want to sync them.