Amazon offers the Toshiba 14" 720p USB Portable LCD Monitor, model no. PA3923U-2LC3, for $178.98 with free shipping. That's the lowest total price we could find, outside of the mention below, by $4. (We saw it for $13 less in October.) It connects to your computer via USB and features a native resolution of 1366x768 (720p), 400:1 contrast ratio, 220 cd/m² brightness, 16ms response time, and more. It doesn't require an AC adapter.

A close price: TigerDirect charges $179.99 with free shipping.