Fastest-booting OS?

I'm soon going to have my own laptop. I plan on installing XP and Ubuntu, but it occured to me that, being it something I'm likely to carry places with me, I could use a really fast-booting OS to use anyplace or to show something to someone.

So, what fast graphical OS does /comp/ recommend?

Do Linux from scratch and you can tweak yourself a functional graphical system that boots from the cold in seconds. Of course, you won't get any hardware detection routines.