Cinch is a new Mac utility from Irradiated Software. It helps keep your desktop windows organized by snapping them into predefined sizes and locations when you hold them near an edge of your screen. While its toolset is limited in comparison to its big sister, the keyboard-based SizeUp (which we covered a while back), Cinch is designed as a quick-and-easy window organization tool for users who prefer to stick with their mouse for such things.
When you run Cinch, it shows up in your menubar. When you drag any window to a top, left or right edge of the screen, it "snaps" (or cinches) to take up the full width or height of the screen: top half stretched horizontally if dragged to the top, and a vertical half for left or right. It's handy, and it's easy to get so used to it that you forget it isn't built into the operating system.
Cinch works with multi-monitor setups, and there's no configuration necessary. Just run it and start dragging windows where you need them. Cinch is available for download as a free trial, and a license can be had for $7US.