One of the most popular categories of Gems is utilities that make it easier, faster, or simply more convenient to arrange windows on your screen—for example, to line up two Finder windows for easier file management, or to stick a Web browser and a text editor side-by-side to preview some Web code. I’ve covered a slew of these utilities over the years, including Cinch, TwoUp and SizeUp, MercuryMover, Zooom, MondoMouse, and Fiwi. But the past few months have seen a veritable glut of new window-management software. I’ll be taking a look at the best of these utilities over the next few weeks; today I start with ManyTricks’ Moom (Mac App Store link).

Like many similar utilities, Moom’s goal is to make it easier to put windows in commonly used configurations—specifically, taking up exactly half or a quarter of the screen, or zoomed to fill the entire screen. But Moom’s standout feature is that it uses Mac OS X’s own interface for zooming windows: the green “zoom” button in the upper-left corner of every window.

Move the mouse cursor over this little green circle, and after a short delay—1/10 of a second by default, but you can make the delay shorter or longer—a small row of iconic buttons appears, each illustrating one of Moom’s standard window layouts: full-screen, or filling exactly half of the screen on the left, right, top, or bottom. Click the button with the desired window layout and, like magic, the window is moved and resized appropriately. If only the zoom button really worked this way.

But there are a couple not-so-obvious options here, as well. Click-drag one of Moom’s half-screen buttons, and its icon changes ever so slightly to indicate that you can reposition the window to fill a quarter of the screen. You can choose either of the corners contained in a button’s half of the screen. So, for example, the “top half” button gives you options to put the window in the top-left or top-right corner.

Similarly, if you’ve got multiple displays, click-dragging a button towards a different display gives you the option of zooming the current window to a half- or quarter-screen size and a particular screen location, but on the other display.

If you’ve previously used Moom to zoom a window, that window’s Moom pop-up panel is slightly different. The icon indicating the current window position is highlighted, and a new Undo (left-facing arrow) button appears. Click this button, and Moom restores the window to its original location and dimensions. Unfortunately, if you manually move or resize a window after using Moom to zoom it, Moom won’t be able to restore it to its original location. This limitation can be frustrating if you accidentally click the standard zoom button instead of hovering over it—do that, and Moom forgets the original position. It would be great if Moom offered an option to disable the standard zoom functionality completely, especially considering that you’re unlikely to use that button if Moom is running.

But what about those of us who prefer to use the keyboard whenever possible? Moom provides keyboard controls, as well. In fact, you get a couple additional options when using the keyboard. Press Moom’s keyboard shortcut, which you define, and a Moom overlay (bezel) appears on your screen. Using the arrow keys—alone or modified with Command, Option, or Control—you can then perform a number of actions: move the current window, at its current size, in 50-pixel increments (hold Shift to move in 1-pixel increments); move the window to another display; or resize the window to fill half of the current screen—up arrow for the top half, left arrow for the left side, and so on.

Once you've used Moom to make a window fill half the screen, you can continue to use the arrow keys to “shrink down” the window to fill just a quarter. For example, if you press the down-arrow key to make a window fill the bottom half of the screen, you can then immediately press the left-arrow key to shrink that window to fill just the lower-left quarter.

In addition, you can configure the Return, Space, and Tab keys to perform actions whenever the Moom overlay is displayed. The options for each include zooming the current window to fill the screen; moving the window, at its current size, to the center of its current display; or reverting the window to its original size and location.

While Moom doesn’t offer as many options for keyboard control of windows as MercuryMover, which also lets you configure presets for specific locations and sizes, Mercury Mover doesn’t offer Moom’s half-screen features. And overall, Moom's keyboard features work well, although it takes some trial and error to get the hang of switching between half-screen and quarter-screen sizes.

If you prefer to use only one of Moom’s control methods—mouse or keyboard—you can disable the other completely. You can also choose to run Moom as a traditional application (its icon appears in the Dock and it has traditional menu-bar menus); a menu-bar utility (you access settings via a systemwide menu); or a faceless application (you access settings by double-clicking the Moom application icon in the Finder).

Moom’s biggest limitation is inherent in its design: In order to keep it dead-simple to use, Many Tricks has restricted Moom to resizing and moving windows to half or a quarter of the screen. But if those windows positions are enough for you, Moom is mighty appealing.

[If you’d like to try Moom before purchasing it, ManyTricks offers a trial version for download from the company’s Website.]

(Disclosure: Former Macworld editor Rob Griffiths is now an employee of Many Tricks, the developer of Moom.)

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