Dropbox - Awesome.
TotalFinder - which is a finder replacement that gives you tabs and a few other neat features. I don’t really need the icon but it gives me a quick way to relaunch the program if/when it crashes.
Flux - Automatically adjusts the screen temperature (I believe that’s the correct term?) of the screen to coincide with the time of day. Basically makes the screen easier on the eyes at night.
- Quick one-glance check for new mail.
Evernote - Don’t really use it anymore, but it looks cool :).
Caffeine - Keeps your Mac from going to sleep. Great for me cause I do some music performance (Reason w/ midi controller) with my Macbook so sometimes it is sitting open on stage for quite awhile unused- and caffeine makes sure it doesn’t go to sleep at an inopportune time.
- Notifications of various sorts.
Lock - This is an OS X icon, I added this little guy from Keychain Access utility (not third-party- it’s in the utilities folder) - in the preferences for Keychain Access there’s a box to “show status in menu bar”. The lock shows if keychain is enabled or not. BUT the real reason I added it was because it gives you one-click access to lock the screen!
Displays - I know it’s hokey ‘cause I’m on a Macbook Pro, but I connect to external displays a lot and this gives me quick access to change the resolution of an external display to make sure it matches native. 
Then, you got your Wi-Fi, Volume, Battery (showing minutes remaining- invaluable IMO), and Date/time. I’m kind of scatterbrained so I love having the day of week, date, and time right there.
(From Kraig Hufstedler)