Today’s computers are marvels of technology that can perform more tasks—and more different kinds of tasks—than ever before. Not only that, but your Mac can be doing more and more of those tasks simultaneously; you can have 15 or 20 applications open without the computer even breaking a metaphorical sweat. Ironically, all this activity is enough to drive you to distraction, potentially reducing your productivity.
If you’re the type to be affected by such visual noise, one solution is to use applications that actually take over your Mac’s screen during use; for example, WriteRoom is a full-screen word processor that obscures everything behind it. Unfortunately, there aren’t too many of these apps out there—chances are, your favorite app isn’t one of them. You could instead use Mac OS X’s Hide Others command every time you switch to a new app, but that’s a hassle (and if you’ve got a messy Desktop, Hide Others won’t hide that).
An interesting alternative is Freeverse’s new utility, Think 1.0 ( ; free). Put simply, Think lets you concentrate on a single application by obscuring all others.
When Think is running, bringing it to the front—either by clicking its icon in the Dock or by pressing Command+Option+Return—displays Think’s Illumination Panel. Looking much like OS X’s own Command+Tab application switcher, the Panel displays the icons for all running applications.

Click on an application icon with the mouse (unfortunately, you can’t use the keyboard to choose), and that application is brought to the front, with all other apps hidden behind Think’s opaque backdrop.

You can then work, undistracted, in that app. You can switch to a different application by again bringing up the Illumination Panel. (Quitting the “illuminated” application automatically displays the Panel, as well.) Think’s Dock icon always includes the icon of the illuminated application to help you keep track.
Note that if you click on an application in the Dock, or choose a new application using OS X’s Command+Tab application switcher, you won’t switch to that app in Think; both the current, Think-highlighted application and the newly-chosen app will appear in front of Think’s backdrop. (Freeverse calls the latter app a “guest” app.) Although this behavior seems a bit confusing at first, it’s actually useful, as it lets you concentrate on multiple applications—say, a word processor and an outlining utility—while other applications remain obscured.
At any time, you can “refocus” Think on the originally-chosen application by clicking anywhere on Think’s backdrop or by pressing Command+Control+Return; any guest applications will be sent behind the backdrop again. Alternatively, if you’re working in a guest application and you want to focus Think on that app, just press Command+Option+Tab; the guest app will become the iluminated app, and the previously-illuminated application will be obscured.
Whenever Think is running, a small control panel floats on the screen; you can place this control panel wherever you like, and it remains translucent unless your mouse cursor is moved directly over it. This panel offers four simple controls: a quit (X) button, a color button (which brings up OS X’s color picker so you can choose a different color for Think’s backdrop), a translucency slider (which controls the translucency of Think’s backdrop), and an Illumination Panel button (which, as its name implies, brings up the Illumination Panel).

As a standard application, Think is subject to Expose, which means that if you need to access something on the Desktop, or to switch to a particular window in another app, you can easily do so. You can also hide Think, using OS X’s standard Hide command, to get Think out of the way without quitting it.
(A bonus feature: like Backdrop, Think is also useful for taking screenshots—it’s a quick way to unclutter the visual background.)
All of this may sound a bit confusing, but Think is actually fairly simple to use—the keyboard shortcuts are especially useful—and you’ll get the hang of it after only a few minutes.
What’s not to like? There are a few things I wish Think did a bit differently. For example, as I mentioned above, you can’t use the keyboard to highlight/choose an application in the Think panel; you must manually click on an icon. And the panel itself doesn’t appear if you switch to Think using OS X’s Command+Tab application switcher. If these two capabilities were included, those who prefer using the keyboard to a mouse/trackpad would find Think even more appealing. It would also be great if you could Command- or Shift-click multiple apps in the Think panel in order to work in them simultaneously, rather than having to choose one in Think and then manually bring the second forward by choosing it in OS X’s Dock.
And, of course, the idea behind Think isn’t for everyone. But if you find yourself easily distracted by the multitude of apps running on your Mac, Think is a unique and useful tool.
Think requires Mac OS X 10.4 (Tiger) and is a Universal binary.