Well, most of the docks do just that.. find an edge and dock to it. If you want something that floats toward the center of your screen you would probably most like right click or tab launchpad. Right click is always there, you only have to click on the desktop and it will be there under your mouse. Tab launchpad stays where you put it but it might not be able to do system commands. Object bar might also be a solution for you but I don't know for sure that it floats like t hat. And you might find a widget that does what you want. I just cant think of any right now.
All of these are permanent in that once you build them and save them they are there until you change them.
