|Why They're Hot:
Fashion Playtes.com strives to be, according to founder and president Sarah McIlroy, a "sticky" e-commerce site. That means keeping its customers—preteen girls shopping for clothes, perhaps under the watchful eyes of their mothers, to whom the site devotes a blog—on the 4-year-old site for a hour per visit. The web-only retailer lets girls play fashion designer in its Design Studio, where shoppers share their apparel collections and buy their creations. The retailer also enables shoppers them to share what is trendy among their school yard set and also to vote on what the retailer should sell. "The key challenge that online retailers will face as the younger generation matures is how to keep them engaged with their brand and on their web site," McIlroy says.