Had a spot of trouble with a hard drive at work today and decided to see what thumb drive Linux is like these days. I found a program called YUMI (Your Universal Multiboot Installer) at pendrivelinux.com and discovered that it's pretty great.
YUMI is a simple Windows executable. It's got a long list of Linuxes -- Ubuntus, Fedoras, server OS's like CentOS, small OS's like Damn Small Linux and Puppy, and non-Linuxes like FreeDOS, as well as special-purpose diagnostic software like Ultimate Boot CD and various AV vendors' recovery discs.
Click on one of the supported OS's, point YUMI at an ISO, and it'll install it on your thumb drive -- as many as will fit, with GRUB to select which one you want at boot time. Better still, if you don't have an ISO, it's got a one-click download for every single one of them.
And while it's got dozens of supported OS's built in, it'll do arbitrary bootable ISO's, too; I tried two and found that one (the latest FreeDOS installer) worked while the other (Hitachi Drive Fitness Test) did not.
As for Puppy, it's definitely seen some progress in the years since I last used it but my gripes remain much the same: instead of programs being labeled by name, they have generic descriptions (hypothetically a good idea for neophyte users who don't know what Seamonkey is, but in practice I think "Web" would probably be a better name than "Browse"), and the package management system is less than entirely intuitive. Still, for coming in around 100MB it's a damned impressive, and a whole lot easier on the eyes than the last time I tried it.
Anyway, YUMI's made it easy enough to set up that you can easily spend a couple hours (or more) screwing around with various USB bootkits. It's an impressive piece of software and one I'll definitely be keeping in my admin toolkit.
(There appears to be a Linux equivalent called Multisystem LiveUSB Tool. I haven't tried it out yet so I can't vouch for it, but if you're looking for, you know, a Linux tool for Linux, that might be something to check out.)