HotHardware have a review of a unique device called the Trios RX-910T6 Hard Drive Selector. Manufactured by the Romtec Corporation, the Trios promises to make the practice of multi-booting your rig as easy as pie. Heres a bit:

    The Trios RX-910T6 is a hardware solution that allows a user to switch between multiple bootable drives with ease. Although the practice of multi-booting a computer system is nothing new, it is more common to install multiple O/S's on a single drive using a third party boot utility. With the Trios RX-910T6, a user can use multiple drives to achieve a multi-O/S system with the added safety of isolating the O/S's from each other. Using separate drives with the Trios RX-910T6 essentially turns a single computer into three separate machines, offering greater flexibility and safety.