I bought my wife a pair of Nashbar shopping panniers. We are pleased beyond expectation with them. They are sloppy and ugly, but they were cheap, and they're very convenient. They're lightweight, and they go on and come off very easily. I think I paid only $50 for them. They work much better than the Basil panniers I have and paid more for.
http://www.nashbar.com/bikes/Product...2_172282_-1___
They're uglier in person than on the web page.