Over the years I drift back and forth between a fully stuffed, full Mac menubar and a sparse, empty one. Currently, I have a nice group of applications that make life a little easier, make work a little quicker. I give you my menubar application rundown.

First up is Divvy, a handy little application that allows you to quickly resize windows exactly fit against each other. Doesn't seem like a huge deal, but I recommend the demo. If you love it, you'll love it. If you don't get it, it's not for you.
Second is TouchOSC bridge, a geeky little application that interacts with TouchOSC app on my iPad / iPhone. I'm just starting to play with it, and it allows the iPad to act as a customized control surface.
Third, Dropbox. If you've never heard of it I'd be surprised.
Fantastical is the next application in line. Though I'm a big iCal fan, that control+opt+SPACE shortcut is killer for quickly displaying your calendar and adding an appointment.

Next up is Radium, a web radio application that sits neatly in the menubar and streams stations.

Alfred is an application, file, script, everything-else launcher that is invoked with opt+SPACE and allows you to type in the application you'd like to launch. It has all sorts of other handy tricks (like math equations, direct access to contacts via Address book, system commands). Found this article as well to help you get started.
CloudApp, lets you drag a file (<25MB) and upload it, then copies the link to your clipboard. I find it useful for sending files in emails so I don't weigh the email down. Likewise, you can toss a file there, then distribute it via IM or Twitter, and I even upload all the images for avclub.us to CloudApp.
LogMeIn, an oldie but goodie, is still the most reliable remote access application I have found. I use it from iOS to remote in to my machine from afar.
Bluetooth, Messages, Wifi… everything else is stock OS X.