A very common UI element found in many applications are those little square handles around an on-screen object that allow you to move & resize it. I haven't been able to find anything like that pre-built in flex, so I've started a project to develop one. It behaves as a container object so you can put any other flex component inside it and get the resizeable functionality right away.

Official website at: http://www.rogue-development.com/objectHandles.xml