I just bought these on eBay, to make the kind of errand-running I'm likely to do easier. I have a rear seat post rack on my Bianchi, and managed to carry a lot of stuff just by lashing it to the rack with a cargo net, but I think the grocery bag panniers will be handy.
*Cough cough sputter cough* on the shipping cost, but my maximum bid was set to approximate the original retail cost, with free shipping. Even though the bags are well-reviewed almost every place I could dig up, they are no longer available, so my bidding strategy seemed reasonable.
Now I just need to come up with a set up for transporting my morning caffeine.