My brother has some KVM switches at work that use cat-5 for KVM extension. It doesn't actually use TCP/IP, so you can't run it through a network or anything like that, it just converts the monitor/etc. into a single RJ-45 jack at one end then back at the other end. Seems to work pretty well for relatively long distances to give you a hard connection to the server room (although it's probably not good for the full 100M of cat-5). It'd be a good excuse to wire your house for ethernet if you haven't already.