Your keypad can move and resize windows, with FreeSnap
With FreeSnap you can use hotkeys to center windows or send them to all corners of the screen. You can use the “plus” and “minus” keys to resize windows without clicking and dragging.
If you think about it, the number-pad makes an easy template for remembering how to size and move windows. The arrow keys size windows, and the corner keys (7,9,1,3) move windows to the corner of the screen.
The “5” key on the number-pad centers the window on the screen without resizing it. The number-pad “Enter” key will maximize the window when it is normal size and vice-versa. The “0” key minimizes the window. When multiple monitors are detected, FreeSnap remaps the “5” key to move the window from one monitor to the next.
FreeSnap has an undo option as well. If you repeat the last command, it will undo that command. There is also an alternate set of keys that are more suitable for laptop users. Unfortunately you can not define custom hotkeys (I hope this option will be added in the future).
To use the mouse for these and more functions, check the free Window Manipulator.