I tried the SliTaz Linux distribution.
Advantages: Iso file only takes up 30Mb; boot is fast; good selection of programs in default despite small size of distribution; program-loading occurs at lightning speed; interface is decent.
Cons: Unable to make wireless work. I tried loading the module for my wireless card, as per instructions, but with no success.
However, should I be able to enable wireless, the distribution will be perfect for its class. I might install it on my mother's old laptop as an alternative to Windows, which is riddled with problems and gives me an enormous headache.
I encourage you to have a look at the SliTaz distribution. http://www.slitaz.org/ (Also see Youtube videos if you want it see it in action).
Downloading it and trying it out on USB is easy!