multiboot Linux tools and other bootable stuff on one USB drive?

Ok, might sound a bit odd. however I use a few different Linux and windows based self booting tools for working on fixing/diagnosing computers.........

I was wondering if i could partition (s) a large USB flash drive and install my bootable tools, with some kind of bootloader.......including a PartPE image....... and of course a menu (like grub etc).

anyway thought i would ask since it is something i have been looking to do for awhile, just have not found anyone else that has done this..... yes i know you can only have 4 primary partitions just want some ideas.

Please don't misunderstand, i have and do make bootable tools..... would just rather carry one flash drive........ rather then one flash drive and CD's......

This is quite a question, so if several web site links is the best answer with a brief description, then I would appreciate that as well. If it's some kind of bash shell thing, thats fine too.

my current primary computer that has a burner is Ubuntu 10.04. i also have access to OSX and windows machines.

I can use a regular 2.5" USB external hard drive if that would matter. (my tools are only bound to get greater in size so why not).