How many monitors do you use on your computer? Probably one. Multiple computer monitors increases screen space and helps to dramatically increase productivity. Jeff Atwood recently joined the Three Monitor Club, which includes computer users using 3 monitors and says that Larry Page and Bill Gates do the same. Though two monitors are well recommended to increase productivity, he says three monitors are even better.
Its not difficult to fix up multiple monitors, you just need the right hardware and fix them up to reduce eye strain. Microsoft has a nice article about using Multiple Monitors with Windows XP. How many monitors do you use?