Microsoft research corroborates what I already knew. Two screens are better than one! For the last 6 months now I've been using two LCD screens on my development computer. I already had a 19" LCD, and I spent another $300 and got a second, 15" LCD. It turns out that my Dell already had a display adapter with two outputs (one digital and one analog) so all I had to do was to plug the new display in! (I got this idea from Rafe Needleman, by the way.)
It's an amazingly productive setup. It's far cheaper than having a single huge LCD, and in a way it's better because it naturally helps you organize your desktop(s.) The left screen has my development environment, the right screen has JavaDoc. The left screen has the email I am writing, the right screen has my inbox. The left screen has... You get the idea.
Next time when you find yourself moving windows around and up and down and sideways so you can see two distinct things at once, remember that you read this and go out and get yourself a cheap second LCD.
What does Microsoft have to do with this, you ask? Well just today I read an article out of Microsoft research where they scientifically tested this setup and found indeed increases of between 8% and 50% in productivity. What they found is what I found, "Once you try it, you never go back!"