Laptops are portable, but they have one major disadvantage: relatively small screens. Fortunately, it is easy to add more screen space by plugging in an external monitor when you are at home or in the office, then leaving the monitor behind when you are on the road.
To achieve this, you need to get a monitor that can be driven from the limited selection of ports that your laptop offers. Most laptops offer a single video output, which is usually a DVI, HDMI or DisplayPort output. Some models (such as Apple's Macbook Air) offer a mini DisplayPort, which requires an adapter cable to connect to a full sized DisplayPort input.
Another simpler alternative is to get one of the new breed of USB monitors. These run everything off a single USB connection: video, audio and power, which makes them very easy to plug in and remove. They are also mostly small and light, which helps if you decide you need the space on the road and take them with you.