The document below provides minimal instructions to create a bootable thumb drive using MultiSystem that will allow you to boot to .iso images on the same drive. MultiSystem is open source software that gives you an easy and convenient way to carry around multiple installation .iso files. It's great for Install Fests or to use as a means to run a Live LINUX instance of any version you may need.
While MultiSystem may have other uses, functions, or tools, these instructions are limited to just the multiboot aspect. If you are using the bootable USB you created on a Windows 8 platform (or any system with UEFI/Secure Boot), check out the article posted by wmack here: http://www.azloco.org/node/197