If you use Time Machine on your mac and store those backups on an external USB hard drive, rather than Apple's 'Time Capsule', you may not want to see that connected drive on the desktop and in the Finder. While you can chose not to show hard disks on the desktop in the Finder preferences, this is an all or nothing approach and I quite like having quick access to connected drives this way. Thankfully, there is an answer and it comes in the form of another Automator Application.
Time machine's backup and restore will still continue to function as normal, this will only hide the hard drive icon in the Finder. To hide the drive, run the app and click 'Hide'. To show the drive again, just run the app again and click 'Show'.
Note that for this app to work, you must name your hard drive 'Time Machine HD'. Alternatively, you could also tweak the app in Automator to work with any name you chose.