there is a service called PiP (Picture in Picture) which is often used for video surveilance.. a few LCD monitors (usually the more expensive ones) have PiP inbuilt. it lets you use the standard connections (VGA, DVI, etc) on your LCD to feed a second image, with its own resolution, in a pre-set PiP viewing area on the monitor. basically like a small monitor inside the main screen. the image isnt resizable or movable, though.

you can also get dual and quad screen "splitters" that divide an existing LCD in 1/2 or 1/4 with their own inputs and separate resolutions. again, though, the devices are ridiculously expensive.

EG - http://www.42u.com/nti-splitmux-dvi-4.htm - $4,000US.

im still not sure WHY exactly these devices cost as much as they do. i did a lot of research before buying my new multiboxing rigs, hoping i could manage a split screen setup for exactly the reason you mention, xzin.. viewing multiple LCD's at once is very inefficient. every solution i came across cost more than all 4 PC's (with monitors) combined =/ it doesnt make sense to me that a unit meant to cut down on monitors costs significantly more than the multiple monitors its meant to replace.

i suppose you could try an LCD with native PiP technology (there are ones that let you split the screen equally in half vertically or horizontally.. many only allow for a small 'box' in a corner for the secondary input.. not comfortable viewing imo), 2 of them would cost roughly the same as 4 cheaper models and youd cut down on desk space used and view radius. 2 split screens and a full screen for your main account. 3 monitors is much more comfortable viewing than 5.