Rclone ("rsync for cloud storage") is a command-line program to sync files and directories to and from different cloud storage providers.
Mount NAS, Router, Google Drive, OneDrive and Dropbox to a network drive on File Explorer. No need for synchronization and no need for web browsers!.
Air Explorer is an application that manages easily all your files in cloud servers (Google Drive, OneDrive, Dropbox, Mega, Box, Mediafire, WebDAV, Copy, Yandex,...) and FTP and SFTP services.
Unify all your storage. odrive makes it easy to access, sync, and share all your files from one place. Integrations to 20+ services, desktop sync, CLI (inc. Linux), placeholders, zero-knowledge-encryption, web client, advanced sharing, and more.
Storage Made Easy provides a software solution, the Enterprise File Fabric™, which unites on-cloud and on-premises file and object storage infrastructure indexing file and object metadata and content.
It's free app, which can combine cloud drives for Dropbox, Box, Google Docs, SkyDrive, SugarSync, FTP, etc, so that you can merge them together and centralize management.