You possibly lost them by Option-Dragging them off.
If you're on Tiger...
Clock: System Preferences > Date & Time > Clock > Show the Date & Time.
Airport: System Prefereces > Network > Airport > Show Airport Status in Menu bar.
If you're on Leopard, then I don't know exactly but you get the general idea.
HTH
SL
EDIT: gr8tfly is just quicker on the draw that me this evening!