You can use mover to easily copy all your files from one cloud storage service to another, over the cloud.
Copy Files Between Dropbox, Google Drive & SkyDrive
Mover.io is an online service that helps you easily transfer files and folders from one cloud storage service to another. The service works on a freemium model – you can transfer up to 10 GB of data for free and then pay $1 per extra GB of transfer.
Mover has connectors for all popular cloud storage providers. You may copy files from your Google Drive to Dropbox, from SkyDrive to Box or even from your old Google account to the new one. They also support FTP allowing you to directly transfer files from Google Drive or Dropbox to your FTP server, over the cloud.
There are no restrictions on individual file size limits (except for SkyDrive) and you may transfer unlimited number of files. Mover creates a mirror copy of your folders on the destination service but if a folder on the source drive has too many files, you have an option to zip them all in a single file before the transfer.
The activity log (see next screenshot) in your Mover dashboard offers a near real-time view of ongoing transfers and the service also sends a detailed email notification when a transfer job has been processed.
Mover.io can also be configured as a backup service for your online accounts. Thus, if Google Drive is offline for maintenance, you’ll still be able to retrieve your important files through Dropbox or Amazon S3.
Otixo is another alternative to Mover though it is more of a unified manager for your various cloud storage accounts.