Laptop with two external screens
I use my laptop as my primary work/study/home PC. The laptop itself has a fairly small 13.3" screen but compensates with a high resolution of 1440x900. At work I also have a 17" Dell desktop LCD with a native res of 1280x1024. I've been using this as an external second monitor for a full year now. Doing this is simple enough, just plug in the VGA cable into the laptop's VGA port, hit WinKey+X in Windows 7, choose connect display and select extended desktop.
Extending the desktop on two screens allows you to move application windows between the screens freely, so you could have say Firefox open and maximized on the external screen and Microsoft Word open and maximized on the laptop screen. The productivity gains from doing this are quite significant. Instead of having to Alt+Tab between applications you can just move your gaze from left to right. This doesn't sound like much, after-all hitting Alt+Tab only takes about half a second. Switching gaze however is far less intrusive on your though process and allows you to retain focus much better.
So if having two screens is good, three must be even better, right? Only problem with connecting a second external screen is that my laptop (and most laptops ever manufactured) only have one VGA port. Fortunately though, all is not lost. Here's where the Skymaster USB to VGA Adapter comes in, or more accurately USB to USVGA as it supports a maximum resolution of 1600x1200. The device is basically a small external video-card that connects to your PC via USB and has a VGA port attached to it (or DVI/HDMI via an additional bundled adapter).
I had my doubts as to how well this would work, especially after reading some old articles about similar products where the image was choppy and low res. I bought it anyway though, and glad I did! Setup was extremely easy. Just take it out of the box, throw the driver CD that comes with it in the bin, connect it to the laptop via the supplied USB cable, let Windows 7 automatically detect the device and download and install the needed drivers, connect the screen, hit WinKey+X again, choose to connect display, select extend desktop and you're done!
You may also want to right-click the desktop and go to screen resolution, then make sure the two external screens are both running at their native res, and also drag the screens to position them in the right positions relative to their real physical locations (Windows got this wrong by default (it's impossible for it to detect) and my mouse would move through the left edge of my laptop screen and appear on my right monitor).
Performance-wise, the USB to VGA adapter is good but not perfect. When moving the mouse pointer there's a slight microsecond lag at times, but it's barely noticeable. Otherwise image quality is as good as the other external screen, running at 1280x1024. YouTube videos seem to play without any noticeable lag, although I'm not sure how well a full screen DVD quality video or a game would play. Having said that though, my laptop has a 1.2GHz ULV CPU, so maybe this would work better on a more powerful machine (I notice more cursor lag when my laptop is busy doing other stuff so it's probably using some sort of software emulation).
As for productivity, it's the bees knees! I can put my Chrome browser on the left screen, my Netbeans PHP development environment on my laptop screen, and my Firefox browser pointing to my development site on the right screen. This way I can quickly Google some APIs and code snippets, copy-paste over to my development environment, hit Ctrl+S to save and look over to the right where I refresh my development page and see the effects immediately. Sweet!