Phoenix Technologies anounced their HyperSpace software now works with ARM processors, so it will be available for very cheap netbooks. HyperSpace is a Linux-based OS which boots very fast, so you it's an almost "instant-on" Operating System.
HyperSpace includes several essential programs like Firefox, Skype & media players. You can also use it to startup your "regular" operating system, like Ubuntu, or XP. So for example you can check your email while the other OS loads in the background.
Be aware though it isn't free, like most Linux distros. Look here for more information.