We have the MindStor 10GB by Minds@Work. It seems to work well enough, although the battery only lasts for about 5-6 GB of transfering. I have a fancy battery charger for my radio controlled model airplanes that I use to charge the battery on the road, but others may wish to purchase or make a second battery pack (6 cell AAA-size 700mAh NiMH).
Cards are transfered by putting them into the device then hitting the "Download" menu on the MindStor. A 512MB CompactFlash card is done in about 6 minutes. We have another CompactFlash card to use while the other is transfering for non-stop shooting.