CloudGopher!

odrive is a free application that makes it easy to manage, access, and share all of your files from one place. Integration into more than 20 services, full bi-directional desktop sync, placeholder files, a robust web client, and advanced sharing capabilities.

Rclone is a command line program to sync files and directories to and from:- Google Drive- Amazon S3- Openstack Swift / Rackspace cloud files / Memset Memstore- Dropbox- Google Cloud Storage- Amazon Cloud Drive- Microsoft One Drive- Hubic- Backblaze B2- Yandex Disk- The local filesystem

Otixo connects your favorite services (like Dropbox, Box, Google Docs, MobileMe, FTP, etc.) so that you can access all your online files in once place.

Integrate Box, Gmail, Salesforce, Google Drive, Dropbox, Basecamp, Evernote, and more. Real-time synchronization and backup of files, emails, notes, and projects between multiple Box, Gmail, Salesforce, Google Drive, Dropbox, Basecamp, Evernote accounts. 15-days free trial.

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.

Mover streamlines the process of transferring your data to, from, and within the cloud. You can use Mover to change cloud-storage providers, back up your website or files, and automate and schedule these processes to make life that much easier.