SizeUp, which lets me position and resize the activate window with customizable keyboard shortcuts. One common use case is to make one window take up the left half of the screen, and another the right half, if I'm working on something that needs information from both. http://irradiatedsoftware.com/sizeup/
Zooom/2, which lets me move and resize windows with my positioned anywhere on the window, activated with customizable key combinations. http://coderage-software.com/zooom/index_green/index.html
SizeUp, which lets me position and resize the activate window with customizable keyboard shortcuts. One common use case is to make one window take up the left half of the screen, and another the right half, if I'm working on something that needs information from both. http://irradiatedsoftware.com/sizeup/