They carry it in Harris-Teeter of all places! Around a dollar a pound if I remember correctly. They receive it in five pound blocks, but it sublimates in their freezer. Find a smaller block to start with, you pay after they weigh it. The trouble with it is keeping it from "melting." It doesn't keep in freezer too well.
I've seen people talk about using it for camping. Supposedly they duct tape the cooler shut with it in there, only going in it once a day. It keeps stuff frozen for several days like this (in the desert!) In that same vein, I've heard not to put dry ice into air tight containers as it will still melt causing a pressure increase inside the container until it explodes.
Maybe a bit too complicated for everyday use, but a good excuse to play with dry ice!