KVM with DVI support

[#1]

Dell will sell you a Belkin device.
You'll want a switch (linky) and a set of cables like these I guess.
Dunno if the links'll work - Dell have just done a load of work on their website (at least they've half done a load of work!)
For examples to compare, just go the Dell site and stick DVI KVM into the search box.
Looks like you can get a switch for around £86 plus cables for £14  (plus delivery and VAT)
If you can get em off Dell - you can be sure to find them cheaper elsewhere too I reckon.

[#2]

I have a tft with dvi and d-sub inputs, with a server on one, and my main PC on the other. Granted when you have one keyboard on your lap and the other on the desk in front of you there can be occasional confused moments, but otherwise it works like a charm. There's a 'source' switch on the monitor to change between the two, and I'm quite happy about not paying £100 plus for the price of a keyboard and mouse and a bit of confusion.
Hope that helps,

[#3]

Hardware KVM  :(,  get into the 21st century 
I would suggest using RDP if you are running the server on Windows, and NX (http://www.nomachine.com/) if you are running the server on Linux.
OK, there is also VNC, but its not as good as RDP or NX on their respective OS's. But it is cross platform.
Also if you are running VMWare then you can install the server client package, on a remote machine to control VM's on another machine.
So personality I would use software backed up with  the monitor input select, and swap keyboards. If the USB ports are in an inaccessable place then a couple of extension cables will sort that.
Chilly

[#4]

I just use putty to ssh in, it works fine. If I use screen as well I can start a session logged directly on the linux box itself, log out, ssh from my windows PC and resume it, log out, go to work, ssh in from there and pick up where I left off...
Screen is great. So is putty. I guess it depends how integrated you want.
Oh, and if you were going to have vnc running, you might as well get two monitors and install synergy on both machines - this is a wonderful (and free) app that allows mouse and keyboard control over LAN. It works like windows extended desktop, except if you move the mouse on to the other PC's monitor, keyboard control follows it. Just another thought.

[#5]

No Machine is available as a DEB package.
This usergroup thread may be interesting readding;http://usergroup.plus.net/forum/index.php/topic,4592.0.html
@orbrey
Synergy sounds great, but I have not had the chance (screens) to play with it.
Chilly

[#6]

http://www.maplin.co.uk/Module.aspx?ModuleNo=48548&criteria=kvm&doy=21m8