I know that a lot of blender users and professional animators have a dual screen setup so I decided to try it. I got another monitor, hooked it up and now I am sitting here wondering what to do with the second screen. I mean I can only use blender on one screen. If you use two monitors please tell me what you do with the second screen.
Thanks
Currently with blender you can split windows out of the main interface and put them on the second screen for instance. Also, it’s very useful if you have an image-editing program open at the same time, as you can stick it on your second screen. Or have a tutorial open on the second screen while you work thru it in blender … the possibilities are almost endless …
Dual-screen is VERY nice. 
In 2.5x beta if you split a window while holding Shift, this will create a separate window that you can drag to a second monitor. This could be the UV/image editor window or graph editor window for example.
I recently switched to a dual-monitor setup, and at first thought the same as you. I kept the setup though, but even after a few weeks still didn’t really feel as if I was getting as much use out of the second display. However, one day I only had access to one screen and found that everything felt much more cramped and counter-productive.
Although it may not seem useful at first, after a while you should sort-of ease into using it, until you reach a point where you can’t live without 2 monitors.
When using Blender 2.49 I tend to keep the Blender window on one monitor and a web browser, music player, or file browser on the other. With 2.5x I usually 3D view + Properties Panel in one window and split the Node Editor or UV Image Editor + Outliner into two separate windows on the other monitor.
I find a dual-display most useful when using GIMP or Syntheyes.
GIMP - I have the image + toolbox on one display and layers + navigation + brushes + colours on the other.
Basically, having a dual-monitor setup just lets you spread out more - letting you see more info at once.
I fell in love with dual monitors from the second i plugged the other in.
One screen for 3D view and properties, another screen for node editor, render, etc.
One screen for Blender, the other for skype.
One screen for Games, the other for skype
One screen for Music recorder (REAPER) timeline, the other for VST plugins… Etc.
Can’t live without it actually.
I use the second screen for GIMP, reference images, internet and CPU/RAM/VIDEO usage/temperature monitors.
I recently worked at a studio which used more than one screen at once with their workflow. As soon as I finished that work experience I went out and bought a full HD monitor to work with. I keep saying to people that once you go dual screen you wont be able to go back to single. I feel cramped and slow when Im doing major work on my laptop alone.
Depends on what your doing really??
If your doing blender work then I usually have the largest screen dedicated to blender only, then use my laptop screen for the internet, chat, reference pictures and 2D work.
Its great when your working on something in Blender, to be able to have reference images right there in front of you, and if you need to google for an answer to something or a tutorial to quickly help you then its only a click away, and you can keep doing 3D work while you wait for things to load (really slow internet here Im afraid…)
But yeh most of the time for just general use I’ll have firefox open in the larger screen and chat/random stuff open on the smaller one.
At this point Id love to get a third HD screen to use as well, so then there would be one either side of my laptop. 
I’ll be like this guy by the end of the year I think: