The Garage" (a Microsoft geeks nest).
It would already be great if it was only a software alternative to KVM's but it also allows you to share your clipboard between computers as well.
In my profession, I frequently experiment on one PC and document the operation on another. I'm using Greenshot to capture screens and save them in a central network location, but sharing clipboard is sometimes better as you can directly copy/paste picture, text, anything...into the final document.
A menu option allows to send a screenshot to, or receive it from, another PC, but you also can use the PrintScreen button (or Alt-PrintScreen) to get the screenshot directly in the shared clipboard without always openning 'Paint'. An option to automatically save the screenshots to file would be a nice addition .
All it takes, is to download a tiny file (1.1MB) and install it on each computer. A security key will be created to associate only the computers you choose. From that point, your mouse will be able to travel from one computer screen to another by just crossing the 'border'. You need to ensure that your screens disposition in the "Machine matric" matches the real situation. If needed, this can be adjusted by a simple drag an drop.
Get "Mouse without Borders" here
With its large media coverage, this tool from Microsoft brings an another software under the spotlights to people (like me...) who didn't know that such a solution already existed for quite some time: Synergy, a Multi-Platform (Linux, OSX, Windows) and Open Source alternative, which is definitely worth a try!