I've been trying to make a DVD that would both play in an ordinary DVD player and also boot in to a GNU/Linux live CD when in a computer. Apparently nobody else has wanted to do this because I haven't been able to find any documentation on the net but I have eventually figured out the rather obvious solution! I guess anyone else who wanted to do this probably knew more about mkisofs than I did but just in case there's ever any one else who needs to know how to do this, and doesn't know more about mkisofs than I do I'm going to document it very quickly here. (Also for my own future reference!)
mkisofs -dvd-video -pad -l -r -J -v -V "KNOPPIX" -no-emul-boot -boot-load-size 4 \
-boot-info-table -b boot/isolinux/isolinux.bin -c boot/isolinux/boot.cat \
-hide-rr-moved -o /mnt/hda1/knx/knoppix.iso /mnt/hda1/knx/master
This example obviously takes Knoppix as the Live CD you're attempting to make but it should work for any live distribution that uses isolinux. The only relevant option to change is the -o, which should point to where you want the iso image to be created and the option following that, which specifies the input folder - i.e. where all your files are which you want to be put in to the iso image.
Hope this helps someone,