How to have a multi-bootable USB KEY that has installers for many different OS’s

I own 4 different computers which I often shuffle the primary OS's around on. I specifically use Windows 7 Enterprise (work laptop) Windows 7 Ultimate (my primary desktop) Windows XP (my old laptop) and the Ubuntu distro of Linux (media center).

So, here's the plan, I just got a shiny new 16 GB USB key. I want to put all 4 of these OS Images onto the key, and then be able to boot from that key, and select which operating system I want to install on the system.

I know how to make a bootable USB key, that's easy for me, but I looked around a little and didn't find any software utilities that can help me composite these operating system images into a multi-bootable installer selection, does anyone have any ideas? I'm sure I could probably do something with bootcamp, but I don't really have any experience there, so before I jumped into something like that I wanted to know if the SU community had any better ideas.

I'd like to point out, I'm also more than happy to listen to advice from the community on better ways to achieve this same, or similar effects!

Another thing I'd like to achieve is fully automated installation (especially if there is an easy way I can select profiles, this is system A's profile, it gets this system name, and has these users, etc.)

One last thought, I know there are many tools that can tweak the installer ISO's to embed the Product Key into a Windows OS Image. What are some of the best tools for this?