4 displays on my main workstation.

2 22" 1280x1024's in the center and right; center screen holds the editor and application/page under test. Right display holds a bunch of tiled terminals, debuggers, top, and other status monitor'ish things.

Left 'display' is a permanent fixture of a laptop 1280x800, holding browser windows for documentation and the like.

Far right 'display' is another machine runnin 1024x768, used for distractions. It's slightly uncomfortable to use this machine, as I have to reach over papers and the like to get to the keyboard and mouse, which makes it a bit of a relief to get back to work.

I used to run all four displays off the same machine, but I found I would lose the mouse cursor/focus far too often, and it simply isn't comfortable using the keyboard so far off to the side of where you're looking.

Even though the laptop is pretty close to center, I still prefer using its own keyboard/touchpad to browse docs; the separate window focus makes it a bit easier to go back and forth quickly.

The desk I have is actually fairly small, about 5' wide, but it has a 3'x1' island shelf a foot off the desk that curves around the back right; even though I've got two crts in the mix, they happily sit on the island leaving me no shortage of desk space.