If you have multiple machines but only one set of mouse and keyboard, then you must check out this neat little tool called Synergy. It allows you to seamlessly share mouse and keyboard across machines. It even allows you to copy and paste text across machines.
I have been using it for a few years now and have recommended it to many already. We all absolutely love it. My current set up is a desktop with two monitors and a set of keyboard and mouse connecting to it. Then I have a laptop with another monitor sharing the keyboard and mouse via Synergy with my desktop. This way I can use two machines and three monitors at the same time without any interruption.
I simply cannot imagine my life w/o Synergy. It is technically straightforward but really useful!