What did you want to place in the menu bar? Some applications have the option to add a shortcut to the menu bar. You can hold down command and use the mouse to switch the placement of items in the menu bar.
i stat menus allows you to view cpu, memory, network stats etc and a calendar. this is all that i have. theres also the apple ones like spaces, bluetooth, displays, eject, users etc which arent up there by default.