Hello
I just put puppy linux on a usb memory stick (less than 100Mb) using unetbootin-windows I can't believe how quick and easy it was, the hardest part was getting BIOS to boot from usb, it's also able to save settings for different computers.
unetbootin-windows has a selection of distros to choose from, I was after something small and easy to use, I tried damn small linux (50Mb) first, but quite frankly it's just too basic for me, don't get me wrong it does everything you'd expect from a 50mb distro they've even managed to put firefox on it which probably takes up half the 50mb on it's own.
Puppy linux will also prompt you to encrypt it when you shutdown, now I have linux in my pocket and I've still got about 900Mb free on my memory stick