Oh and just for interest, I got the FAT library compiled and running on the arduino, however I had to do quite a few changes as he uses the C99 standard and I couldn't add that flag in arduino environment. I didn't get it working fully and kept getting a few errors. I gave up in the end because it just fits into the atmega168 memory and leaves little room for anything else. You can only run a few functions before you have no room at all left. It would be good to get it running once the larger size memory atmegas are available for the arduino environment.
Much easier to write to a text file on the memory card, pull it out and chuck it in your computer to read your values! 