Since you want the same screen at all locations you can use a simple amplified VGA or DVD splitter, depending on the inputs you need for the monitors. To do this correctly, all displays should have the same aspect ratio, and ideally should all have the same native resolution (this will not be the case if you mix 19" and 22" displays) => although if you mix displays with differing resolutions (e.g. 1440 x 900 for a 19" widescreen vs. 1680 x 1050 for a 22" widescreen) you could simply use the lowest resolution (e.g. 1440 x 900) for your display.
If you're planning to mix standard aspect ratio displays with widescreen displays, you should really use a dual-monitor PC to create the two different aspect ratio screens ... and then feed each of those outputs to a separate amplified splitter to drive the other monitors with the same aspect ratio.
A couple of examples of what you need:
VGA splitter:
http://www.cablestogo.com/product.asp?cat_id=3416&sku=29552DVI splitter:
http://www.monoprice.com/products/product.asp?c_id=101&cp_id=10113&cs_id=1011302&p_id=4073&seq=1&format=2