SD-Omega SD631T carPC supports 2 monitors

This box is Linux powered, built for use in your car, and manages to drive two displays. It is setup so that you can use the primary display in the front for navigation or something useful like that, and then the rear display for playing a video for the kids or something like that.

Or, you can just extend your desktop, for lack of a better word, across multiple screens. It has an Intel chipset with a 400/533MHz front-side bus and support for your choice of Pentium M or Celeron M chips up to 2.13GHz in speed.

It supports DDR2 and has integrated graphics with DVI, VGA, and TV-out video outputs there is also Firewire port, a pair of PS/2 jacks, Ethernet, and three USB ports. There is also support for an optical drive, but there isn't any price or availability info.

Car PC supports dual displays under Linux [via linuxdevices]