Every app in my MenuBar is used several times per day. There’s no reason for it to be there if it isn’t.
CoverSutra (hidden): A handy and attractive way to control iTunes without ever leaving your current app.
OmniFocus: Perfect for the Getting Things Done® system, but flexible enough for any task management style, OmniFocus helps you work smarter by giving you powerful tools for staying on top of all the things you need to do.
Dropbox: An indispensable utility that allows you to sync your files online and across your computers automatically.
Droplr: The best way to share files from your Mac on the internet. Period.
Caffeine: A is a tiny program that puts an icon in the right side of your menu bar. Click it to prevent your Mac from automatically going to sleep, dimming the screen or starting screen savers. Click it again to go back. Right-click (or ⌘-click) the icon to show the menu.
Time Machine: Automatically saves up-to-date copies of everything on your Mac — photos, music, videos, documents, applications, and settings. If you ever have the need, you can easily go back in time to recover anything.
Airport Utility: Allows you to manage and monitor AirPort Extreme, AirPort Express, and Time Capsule base stations.
Clock
Spotlight: The lightning-fast search technology built into Mac OS X that makes it easy to find what you’re looking for, even if you don’t know where to look. (Note: I keep Spotlight in the MenuBar, and use it occasionally, but predominantly use Alfred.)
App descriptions are adapted from the individual product pages. They are not my own words.
(From Ian P. Hines, Writer, Interviewer, and Communications and Marketing Manager for the Maryland Energy Administration. Also posted on his blog.)