MSI recently announced video card enclosure dubbed Luxium, that houses an x16 PCI Express graphics card which you can then hook up to you laptop's ExpressCard slot, giving you the ability to use a desktop-class video card for your gaming needs. A similar product from Asus called the XG Station was unveiled back in January. Even though the ExpressCard channel can limit the video card performance, many laptop owners will be more willing to buy a video card than a whole gaming desktop computer.
According to the ExpressCard web site, the ExpressCard channel will limit the performance that a PCI Express x16 card offers because it only operates on a single express channel at a data rate of 2.5Gbps.
The Luxium, presented at the Computex 2007, will need its own power source and besides letting you work with your preferred graphics card it offers extra USB and audio connectors. Availability and pricing has not yet been revealed.