If you don't mind erasing the usb stick and just using 300mb of it, it works even easier, as you don't have to format the disk or install the MBR.

Just do:

wget ftp://ftp.debian.org/debian/dists/stable/main/installer-i386/current/i mages/hd-media/boot.img.gz
zcat boot.img.gz > /dev/sda
mount /dev/sda /mnt
cd /mnt
wget http://cdimage.debian.org/debian-cd/3.1_r3/i386/iso-cd/debian-31r3-i38 6-netinst.iso