IOGEAR 8-Port KVM Switch GCS138KIT
While a lot of KVM switches are designed to connect just a few systems, this is a great option if you're looking for something much more extensive. This is an eight-port switch you can use to connect eight different systems to a single mouse, keyboard, and monitor. If that's still not enough, you can use more than one of these switches together to control up to 512 computers all with a single keyboard, mouse, and monitor. It also has an on-screen display that lets you keep track of what computer you're currently accessing.
Keep in mind, this pick is designed for a mouse and keyboard with PS/2 connections (rather than USB) and it uses VGA video ports. You can use this switch on a desktop, but also designed to fit into a rack for professional use. Eight connection cables are included, four of which are six feet long while the other four are ten feet long. This switch is definitely not for an average home setup, but it's a great choice for professional rigs with even hundreds of systems.