SecondBar put the OS X menubar on both of your Mac's dual monitors
SecondBar has a few weaknesses -- it's Snow Leopard-only, and it doesn't copy your extra menubar apps onto the second bar. It does give you access to the Apple Menu and the menubar for the active application, though, which can be extremely useful. it also has keyboard shortcuts to resize and reposition windows to one half of the screen, in case you need to view documents side by side on that second monitor.
Oh, and SecondBar is also completely free. Probably good, considering how pricey those delicious Apple Cinema Displays are.