Mac: Sometimes, you just need help focusing on work, and the menubar can get in the way of that. Menu Eclipse 2 dims your menu bar so you can concentrate on what you're doing.
Menu Eclipse runs in the background and dims the menu bar when you're not using it. You can select the shade and dimming effect, but you can't hide the menubar completely unless you can match your desktop background perfectly. Still, the dimming effect is enough that it gets the menubar out of your way so you can concentrate on work.
If that's not enough for you, and you're on an older version of OS X, you can also completely hide the menubar.