ITreviewed posted a review on the Kensington Dual Monitor Adapter

Kensington's Dual Monitor Adapter is a low-cost way to add a second display. Ideal for laptop users not wanting a raft of features (there are similar products costing twice as much that offer a lot more flexibility), it provides a halfway decent video card that allows you to extend your desktop and get more productivity (and fun) from you machine. Don't go trying to play any graphic-intensive games on it though, you'll be sadly disappointed. It also needs a fairly powerful CPU to work well: Kensington recommends at least a 1.2GHz dual-core CPU. It may lack frills and support for high resolutions, but this USB adapter expands your desktop across an extra monitor for a surprisingly small price.

Kensington Dual Monitor Adapter reviewed