Cinch for Mac
Cinch, developed by Irradiated Software, is an elegant, mouse-driven solution to window management. Inspired by Microsoft's Windows Explorer, Cinch is based off the idea of "hot-zones". Once you drag a window into one of the zones (either left, right, menubar), an outline of your resized window will appear on the screen. Just drop the window into the hot-zone and the application window will be resized. Cinching to the right or left side of the screen will resize the window to exactly half the screen's resolution. The top hot-zone resizes to will the entire screen. Dragging a window away from its cinched position will restore the window to its original size.
You can download the free version (occasional pop-up), or purchase a license for yourself over at the Irradiated Software store. I will be posting a video review of Cinch on my YouTube channel, which can be found here.