There aren't actually many serious and well known producers of slim and light portable USB powered monitors of a decent size other then the offerings from Toshiba and more recently Lenovo which retail for about £170 if not a little more. That is until now, OEM monitor manufacturer AOC is now entering the mainstream consumer segment of the market too with their light weight portable 15.6 inch E1649FWU USB signal connected and USB powered LED monitor. It certainly undercuts the competition by huge margin on the pricing front.

For your money you'll get 1366x768 resolution at 500:1 contrast ratio with 200 nits brightness. Response time is pretty nippy for a USB monitor at 16ms. As you can see from the snaps, its hardly an eyesore. 

There's also a 22 inch version (E2251FWU) that obviously isn't as portable and will cost a little more for the extra pixel real-estate at 1920x1080.