When siblings Dave and Catherine Cook dreamed up a way to modernize the high school yearbook by putting it online, they had two factors on their side: invaluable insight and a big brother, Geoff, who had $250,000 to invest. Only 17 and 15, respectively, when MyYearbook.com launched in 2005, the teens knew what their peers wanted. Says Geoff, 28, "[Catherine and Dave are] so plugged in that we don't need to run focus groups to find out what a good feature is."
Working with programmers in India, the Cooks developed a social networking site that allows its 2 million members--mostly high school students--to create personal profiles, join groups, share school documents and battle for titles like "Best Looking." Its focused demographic has attracted advertising dollars from Disney and Procter & Gamble, helping raise projected 2007 sales to the low seven figures. With numbers like these, the New Hope, Pennsylvania, company is at the top of its class.