I have been looking for that website for so long!!! (maybe I should have created it before those guys to satisfy my need, but never thought about using the crowd at that time - they did it, congrats!)
You can read on their site : "We believe “the next YouTube” is going to be somewhere here, on KillerStartups.com. That’s our goal. We aim to provide you with that info right at the birth of the startup"
To visit the site, click here.