For *nix users, it is possible to boot Spinrite by just writing the floppy disk image of Spinrite to a usb drive.
dd if=spinrite.img conv=notrunc of=/dev/sdx
cat floppy.img > /dev/sdx
sdx is your usb drive. Root privileges required.
If you're feeling fancy, you can also integrate Spinrite onto a syslinux or extlinux usb drive with a boot menu. For example, here's a minimal working
syslinux.conf that also includes memtest on a single usb drive:
menu label Run SpinRite 6
menu label Run MemTest86+
See the syslinux documentation for more details about creating boot menus.