While large (24″+) monitors are certainly enticing, I find that my productivity improves with multiple monitors rather than bigger monitors. My desktop setup includes two 23″ monitors in Landscape orientation and a 22″ monitor in Portrait mode. While most laptop have a VGA, Display Port or DVI output, that only allows you to connect one monitor.
Wanting to have at least two external monitor, I found a great solution from Kensingon that will work on Mac and Windows PC to add an additional monitor (or two or three…) via a simple USB connection. 
At under $60, the Kensington Universal Multi-display adapter works on most recent OS (including the Apple Lion and Snow Leopard, Microsoft Windows 7) is simple to use and just works. The adapter comes with a DVI output and a VGA adapter and support 1080p resolutions (1920×1080) in 16/9 format and 2048×1152 for other aspect ratios.
If you want to add additional monitors, just add more adapters, it’s that simple (up to 6 adapters, that’s 8 monitors total, including your laptop monitor).
Is it fast? It’s fast enough for most tasks. Would I use it for gaming or 3D design? Probably not but it works very well for everything else.
Excellent. I’ve looked for something similar before, but had little luck googling for it, and still less trying to explain it to people in shops.