The coffee cup is an app called caffeine, clicking the menubar icon prevents your mac form going to sleep.
The paper airplane is 'Sparrow'. That's also in the dock because it doesn't have an option to get rid of it.
The music note is 'coversutra' an itunes controller with lots of nice features like universal song switching hotkeys.
Twitter app is also in the menubar because there's no option to get rid of it.
CloudApp is a drag & drop file sharing app and link shortener. Drag a link from chrome (or any browser), it will shorten it. Drag a file, it will upload it and give you a short link. It also ha san option o auto-upload screenshots you take on your mac.
The thunderbolt is is 'Blitz', it suspends all apps but one to save system memory. I use it on photoshop when rendering high resolution images. It focuses all system priority on one app to improve performance on the fly.
The paintbrush is a color picker app. Memorizing hex codes is not easy, this does that for you. Has some other handy features too, like selecting color from your screen with an eye dropper.
145 degrees is my cpu temperature. If I click on that I can change the fan speed. This is iStat Menus.
Then there's airport and other things.
My dock has all my window apps, that have windows and complex interfaces. Things I have to start and stop. Menubar apps are lightweight, simple interfaces, and run all day.
Oh, lol. I have those there for sorting files via drag & drop. If I put my music folder or photography folders in the dock, then I could drag & drop files into their sub folders. This way, if I want to organize a file, (which I do often), I just use a 4 finger swipe up on my trackpad to expose the desktop, drag it from the desktop and hover over one of the folders few a second till it pops open, then drag & drop into the sub folder of my choosing.
The only FOLDERS in my dock are Applications and utilities. And I use it as an application launcher, not a file launcher.