There exists in this world, two very broad categories of individuals--those who have taken to heart "A place for everything, and everything in its place" and then the other 97 percent of us. And while this majority may know in their heart-of-hearts that storing files on the desktop is a poor idea--because it creates clutter and can slow down your Mac--we do it anyway. And for good reasons. There is no more convenient place to put files you've dragged from an application or web site. And pressing Command-D within a Save window to point the application at the desktop is just so easy.
Regrettably, convenient though this may be, the accumulation of files eventually leads to chaos. You can no longer find files you need by glancing at the desktop. While you could vow to turn over a new leaf and file everything correctly, you and I both know that's a pipe dream. These habits die hard. So rather than fight it, let's just find a way to quickly clear the desktop so that you can deal with this cruft at a later time.
That way is Automator. With just three actions you can clear the deck. Like so:
Create your workflow
Launch Automator, choose Service from the template sheet that appears and click Choose. At the top of the workflow area, configure the first items to read Service Receives No Input in Any Application. Select the Files & Folders entry in the Library pane and from the Action pane to the right drag Get Specified Finder Items to the workflow area. In this same Files & Folder library you'll find Get Folder Contents and Move Finder Items. Drag each of the actions to the workflow area in that order.
In the first action, click the Add button. In the sheet that appears select the Desktop entry in the sheet's sidebar and click Add. In the Finder, open the Documents folder in your user folder and create a new folder called Desktop Stuff. Now drag that folder on top of the To pop-up menu in the Move Finder Items action.
Press Command-S to save your workflow and in the sheet that appears, name the service Clear the Decks and click Save. Quit Automator.
Presto, chango, clean desktop!
In the Finder, select Finder -> Services -> Clear the Decks. Plaster a tidy smile to your face as you see everything on the desktop (save any mounted volumes) disappear from the desktop and move themselves to your Desktop Stuff folder.