The Unity grab handles are a nice and easy way to resize windows. To enable the Unity grab handles you need to have the CompizConfig Settings Manager installed.
To install the CompizConfig Settings Manager (ccsm) open a terminal window (press Ctrl+Alt+T) and copy+paste the following line:
sudo apt-get install ccsm
When installed close your terminal window.
To enable the Unity grab handles press Alt+F2 and type ccsm. When ccsm is open click on the Uncategorized button and check if the Unity MT Grab Handles plugin is enabled (if not enable it) then click on the Unity MT Grab Handles button. Toggle Handles is disabled by default and you can enable it by clicking on the first Disabled button and mark the Check box. When enabled enter a grab key combination (i used Ctrl+Alt+Z because they are close to each other and easy to press with my left hand. This way i can still use my right hand to resize the window using my mouse). When done click on the OK button and close your ccsm.
I thought this was set by default. I resize my windows by going to the corner with my mouse and dragging to desired size.
Well … now we can use a key combination to select the window border and resize them using the orange handles … :S