Is there a way to make a bootable USB drive with the ability to install Mac OSx, Windows 7 and a flavor of Linus from it?
i understand bootable Mac OSx would only work on apple hardware, I also know that it is possible to make a bootable windows/linux usb drive, but could not find a way to also add Mac OSx
Sounds like you want a Hybrid MBR. May not work though, there's a lot of issues with them.
Overall, hybrid MBRs should be avoided. I've included support for them in GPT fdisk only because certain popular OSes (read: Microsoft Windows, at least through Windows 7) can't boot from GPT disks on BIOS-based computers. (See the Booting from GPT page for a possible workaround, though.) This fact makes hybrid MBRs a practical necessity in some environments. Apple's Boot Camp, for instance, uses hybrid MBRs to enable Macintoshes to dual-boot both Mac OS X and Windows; and if you want to dual-boot Windows and anything else on a disk of more than 2 TiB on a BIOS-based system, you'll need a hybrid MBR, UEFI DUET, or possibly some other solution I don't yet know about. Older non-Windows OSes (BeOS, OS/2, DOS, etc.) are likely to require a hybrid MBR to handle GPT disks, too, although I haven't tested them explicitly.