To me "the biggest overnight success award" goes to Andrey Ternovskiy for Chatroulette. The site climbed high in rankings fast, quickly started generating profits, hundreds of clones came to life (of none of course got any traction although everyone was making it better), you could buy the "roulette script" online and do your own site, and Andrey score a visa to US to work on some other startups, as far as I know. This, in any possible measures, especially with someone of 17 years old, I personally call "overnight success".
There was also a guy selling pixels, which was stunning to me how his out of box thinking got him a million bucks (he is working on a cool idea raising charity money for Africa now). Of course plenty other similar website popup, but none got traction.