Divvy has a pretty UI to choose the size and location of windows, and puts little buttons in the top corner of windows to change their size and location. Recta

Divvy has a pretty UI to choose the size and location of windows, and puts little buttons in the top corner of windows to change their size and location. Rectangle provides hot keys and an icon in the menu bar to set window size and location. I use rectangle now, but have used divvy in the past and I think is better for people who like to use their mouse vs hot keys.