To move a Gnome panel, you can use the menu option: right-click panel -> Properties -> Orientation. The "Orientation" drop-down has four options, one for each side of the screen: Top, Bottom, Left, Right. However, there is no menu option to move a panel to a second monitor. To accomplish this, hold down alt and drag the panel to the desired location.
I added a Ubuntu Brainstorm idea about this issue and added a possible solution. Go and vote for your favorite solution or add your own: