A decade after pets.com and a string of other early Internet specialty retailers collapsed, a new wave of start-ups — enabled by the power of cloud computing, advanced delivery systems and deep social relationships with customers — is shaping e-commerce.

From diapers and eyeglasses to pool tables and, yes, pet products, entrepreneurs are developing specialty businesses to compete alongside one-stop shopping giants like Amazon.com and Walmart.com.

“There is a new generation — Internet retail 2.0,” says Wharton marketing professor David Bell , noting that after the 2000 dot-com bust, activity in online specialty retailers dried up as financing became difficult, or impossible, to get and industry executives struggled to evaluate failed business models.…