Matt, I can speak highly of Synergy (http://synergy2.sourceforge.net/) as a program you may want to look into using - KVMs are expensive, annoying antiques IMO. Allows the sharing of keyboard, mouse, and other input (e.g. limited clipboard operations) between (networked) computers. I've only ever used it between multiple Windows PCs, but it should work just as well or better under Linux / X as that was what it was originally developed for. The OS X port is "limited" though, so you'll have to try it out and see what it can do.