Dropbox: Dropbox is a free service that lets you bring your photos, docs, and videos anywhere and share them easily.
CloudApp: CloudApp allows you to share images, links, music, videos and files.
: Google Notifier is an application that shows you alerts in your menu bar, so you can see when you have new Gmail messages or upcoming Google Calendar events without having to open a web browser.
Reader Notifier: Reader Notifier aims to supplement the official Mac Notifier menubar plugins for OS X, in adding support for Google Reader. Reader Notifier tells you when you have new unread rss/feed items available, and lets you visit those feeds without ever going to the Google Reader interface.
CalendarBar: CalendarBar is a unique way to keep track of your events. It shows a list of upcoming events in your menubar where it’s easy to access from any application. CalendarBar supports Facebook, iCal, and Google Calendar so you can keep track of all your events with ease.
Spotlight: Hopefully no description is necessary.
All menubar icons are my own customizations and can be downloaded here.
Instructions for customizing your menubar for a black background (directions only for 10.6.*, I am not responsible if you don’t follow the directions correctly) can be found here.
(From Zachary Yocum)