If anyone is on a Mac trying to write the Arch image to an SD card, follow the steps on this site to find your SD card: http://www.embeddedarm.com/support/faqs.php?item=10
The command for me was: sudo dd if=$RPIDIR/archlinux-hf-2013-07-22.img of=/dev/disk1 bs=4m
It also took about 20 minutes to write.