I'm pretty sure I heard about Jettison from Allison Sheridan, but I've been using it for months and had forgotten about it until I was sitting down to prepare for the latest Mac Power Users Episode featuring Mac Utilities. It just quietly sits in my menu bar and does its job, which is what makes it so great. Jettison is a simple application that does one thing well, it ejects your drives.
Why do you need an App for that? Because Jettison does it better. Firstly, Jettison allows you to automatically eject all drives with a single click. You can choose which drives you want to mount and dismount. For example, I almost never want to eject network volumes like my Drobo FS or my shared drive at work so I've specifically told Jettison to exclude those Apps. That's all well and good, but an App like Alfred can be configured with an Eject command to accomplish this.
My favorite feature of Jettison is the ability to automatically eject drives on sleep. How many time have you gone to grab your laptop off your desk and unplugged a drive only to get a dire warning message on your screen? No more with Jettison. You can configure Jettison to automatically eject drives upon sleep. As soon as the computer sleeps, the external drives are unmounted so your an safely grab your machine, disconnect USB devices and go.