Don't let its weird name scare you: Wappwolf Automator for Google Drive is one of the most powerful apps around for dealing with files (and maybe also wolves) in the cloud.
Wappwolf is kind of like an IFTTT for Drive: It allows you to set up recipes for advanced automation based on files being added to specific folders. You could create a Dropbox folder, for instance, and tell Wappwolf to upload any files placed in that folder to a matching folder in your Dropbox account.
Wappwolf also works with Amazon Cloud Drive, Basecamp, Box, Evernote, Facebook, Skydrive, and an array of other services. In addition to cloud-to-cloud syncing, it can automate a variety of Drive-contained actions, such as converting files, removing EXIF info from images, and stamping logos onto images.
The app allows up to 10 automations to be configured for free, with up to 10 files a day being processed. If you want to increase that allotment, you can opt to pay for a higher-level plan (starting at $8 per month).