CD to boot both Mac and PC
Preliminary research suggests it may be possible to boot both Mac and x86 hardware from the same CD. It seems that the boot sector for the El Torito boot disk specification used by most PCs is different from the boot sector used by the Mac.
The gory details
The El Torito standard as implemented on most modern PCs means that the first place the PC goes to find it's boot record is sector 17, after the volume descriptor (stored in sector 16). This entry points to one or several bootable images (images of floppy disks or of other media).
The Mac boot CDs are different. The volume format is HFS. The search for the boot sector begins at sector 0.
There seem to be a couple of solutions (see article above - Bootable hybrid). It looks like a matter of constructing a logical map of the cd and ensuring both Mac and PC boot information is available. PC seems to ignore HFS filesystems and only boot from ISO, so this is good. Mac only boots from HFS, so it must be directed to a bootable HFS volume from the boot sector partition table.
Unix tools
mkisofs
hfsutils
Potential benefits
If you can dual boot from a CD then you can dual boot from a DVD, USB or any other device that uses the El Troito standard.