Hi,
Be _VERY_ wary of KVM switches that use a mechanical turn-knob on the front. These are the cheap kind you can get for < $50. Most of the time its just a rotary switch that switches between the different leads of the monitor cables. This will cause a _noticable_ loss of signal quality and usually leads to ghosting like when you have only an antenna on top of your house for your TV and you don't get very good reception.
On the flip side, most KVM switches with electronic switching (ie no movable parts) are fairly good. Of course, if you want a _very_ good KVM, go Belkin OmniView

But those are expensive and IT professional. Linksys has some good ones (I use a Linksys ProConnect 4-port) and other vendors do too. I have no problems with mine, I share between a FreeBSD server, my G4, and a PC. About $70 from PCConnection I believe.
Keep in mind that the Linksys ProConnect switches have a MALE connector on the switch for each computer (female for the KVM-monitor though), and you've got a female connector on the video card, so you'll have to get Female-Male cables. This is the _opposite_ of what most other places do.
A good place to get cables is
www.cableclub.com. They have pretty much everything, though it may be a bit hard to find. Never had any quality problems with them.
Dan