The Xfce 4 Panel supports multiple panels, with many options for their
position, appearance, transparency and behavior. There are many items
available by default to full fit a panel, like application launchers
with detachable menus, a graphical pager, a tasklist, a clock, a system
tray, a show/hide desktop switcher, and even more. It offers an easy
way to add items using a dialog, and to move items accross different
panels.

WWW: http://www.xfce.org/projects/xfce4-panel/