Dongles to connect 2 monitors to a 13" mid-2010 MacBook Pro (mini DisplayPort)?

Another option to to use a display multiplexer, like the Matrox DualHead2Go DP. This will have much better performance (frame rate / snappiness) than the USB solution, at about 4X the price. It's best with matched dual external displays - or triple; there's also a 3-monitor solution. I haven't used one personally, but have recommended it to clients with success. The reviews are quite good.

An option for this MacBook Pro is to add a USB Video adapter to get that 2nd external monitor. They are available in a wide range of resolutions and connectivity. Not sure which is the best one to buy but here is an example of a USB 2.0 to DVI Display Adapter.