If you want a serious screen on the go, the Philips PET1002 portable dvd player offers you a huge 10.2 inch screen.
Currently the PET1002 is on sale on Amazon.com for $299.99.
The Philips PET1002 plays besides of the shelf DVDs also DivX 3.1 and MP4. The battery life is 5 hours. The weight is 2.6 pounds. Such a portable DVD monster is only reasonable, if you are not traveling with a notebook.