“You can work far more efficiently with two—or better yet—three monitors than with one. But your hardware may not support that many. if you have a desktop PC, you can update the video card, but that’s not an option with a laptop.
StarTech.com manufactures and sells a wide selection of USB-to-video adapters for various configurations. For instance, it offers adapters for VGA, DisplayLink, DVI, and HDMI. Some require USB 3.0—a good choice for gaming, graphic design, or HD video. Some of the USB 3.0 adapters even have USB 3.0 pass-through, so you won’t have to lose the use of that port for other devices.”
Read the whole pcworld.com article on any monitor you can.