Around the CNET office, more and more people are using a two-monitor setup. It used to be a kind of luxury for data professionals -- people with lots of spreadsheets and documents that needed to be open side-by-side. But these days, with more people ditching desktops for laptops, hooking up an extra monitor is just a way to reclaim the screen real estate you lost by going mobile.
Now, maybe you considered a two-monitor setup years ago and got turned off by the idea of installing video cards and adapters. Those days are gone. With any reasonably new computer, you should be able to make this work with just a monitor cable, and a few minutes.
Mac users should check out the Mac version of this tutorial.