For fast loading linux distros for netbooks, maybe look at
xPUD or
BrowserLinux which I think are geared towards running Firefox and (almost) nothing else. (
gOS may be similar.) I've never tried any of them, however.
There are also several linux distros designed mainly to be run from USB or similar which could probably achieve fast boot times, like
Damn Small Linux,
Tiny Core Linux, and Puppy (and variants like
MacPup), which has already been mentioned. I think the smallest linux distro, which did boot insanely fast when I played around with it, is
Slitaz, which does have a working web browser (Midori), but I really can't imagine trying to use for serious work.