DigitalTiger's "SideCar" for laptop multimonitors
http://www.digitaltigers.com/sidecar.shtml
The SideCar is a portable notebook computer accessory that enables you to drive up to four extra displays from a Windows XP/2000 notebook — or up to two extra displays from an Apple PowerBook.
The SideCar attaches to the notebook via a simple PC Card (PCMCIA) interface, enabling easy docking and undocking of the notebook from the multi-monitor display setup. Combined with a notebook's built-in LCD display and external monitor support, the SideCar enables up to six displays to be driven by a single Windows laptop.
Each SideCar display is an independent monitor under Windows and Mac OS. You can run different applications on each display, move your mouse seamlessly across all displays, and even stretch applications across displays.
The following diagram shows how SideCar solutions enable a Windows notebook to drive multiple external displays. (SideCar PlusFour example)