As root (thanks to Austin Che), download and run: http://austinche.name/maemo/getlockcode

Or (showing how stupidly easy it is to get.. thanks Nokia):

sudo gainroot
chroot /mnt/initfs/
text2screen -t `strings /dev/mtd1ro | grep [0-9] | grep -v [a-zA-Z@] | tail -n 1` -s 3