Apple - How to Eject All External Partitions Quickly?

The only caveat to "quickly ejecting" disks with any reliability is that they will not eject if there are files in use which reside on them. That said, you can force eject disks, but that would not be ideal if files are, in fact, in use.

Easiest way to instantly eject all disks is by invoking an Applescript (could also create a shell script, but Applescript is more easily turned into a one-click application solution).

So go to your Applescript Editor, paste in the following:

tell application "Finder" to eject (every disk whose ejectable is true and local volume is true and free space is not equal to 0)

and save the script as an application wherever you choose (do NOT use the /tmp folder as illustrated). Add the resulting application to your Dock, and you have a one-click Quick Eject.

Note: the and free space is not equal to 0 portion is so that the script doesn't eject the contents of your CD/DVD drive. Remove that if you would like any inserted disks ejected as well.

I'd recommend Alfred. It's a quick launching app that includes the feature of ejecting volumes. You can select what kind of targets qualify for the command (network drive, local, etc.).

When you trigger the shortut, you can select a specific volume to unmount. Or you can type ejectall (this shortcut name is customizable).

On OS-X Mountain-Lion, I can option-click one of the "Eject" icons (hold down option, then click the eject icon), and all external partitions will eject.

(Update) This has been verified to also work on OS X Mavericks and even on macOS Sierra, as I suspected it would. It can probably be assumed to work on at least all versions in between (try it out!).