YUMI (Your Universal Multiboot Installer) can be used to create a Multiboot USB Flash Drive containing multiple operating systems, antivirus utilities, disc cloning, and diagnostic tools. YUMI uses syslinux to boot extracted distributions stored on the USB device, and reverts to using grub to Boot Multiple ISO files from USB, if necessary. Aside from a few distributions, all files are stored within the Multiboot folder, making for a nicely organized Multiboot Drive that can still be used for other storage purposes.
YUMI works much like Universal USB Installer, except it can be used to install more than one distribution to run from your USB. Distributions can also be uninstalled using the same tool.