We're all about multi-monitor setups...once you go dual, single feels a fool. But if you're on a laptop, or don't have any slots available for another video card or just are on a budget, then an external USB vid card like this one from UV Plus+ might be the solution for you...
The diminutive USB 2.0 powered accessory uses Displaylinktechnology, supporting both DVI and VGA at up to 1280x1024/1440x900 (UV12) or 1600x1200/ 1680x1050 (UV16) screen resolution. The units are even magnetic, so they can be safely and securely stacked.
* Windows Vista Aero Support
* Windows XP and Vista 32bit Support
* No onboard GPU
* High-Performance DDR Memory
* Uses a virtual driver
* Stackable by design with a small footprint
* Completely silent operation
* Onboard power and status indicator LEDs
* Portable, making it easy for travel
About $81 online, but us Mac users are SOL with no OS X support.
[via Coolest Gadgets]