Square

It's easy to miss given all the trouble plaguing Jack Dorsey's other company, Twitter, but Square has had a remarkably good run of late. When Dorsey launched Square eight years ago with co-founder Jim McKelvey, the San Francisco company focused on selling credit card payment systems to small businesses. But now, Square's ever-popular gadget is just one of its many products. "Today, sellers come to Square for much more than payments and hardware," Dorsey told investors earlier this year.

Square is becoming, in other words, a one-stop shop for small businesses: You can get invoices and payroll services there, or even speedy cash through its lending program, Square Capital, which has extended $1.3 billion since its 2014 launch. And Square has even gotten into the on-demand food-delivery business by buying Caviar. New products launched since 2014 now account for a full quarter of the company's adjusted revenue. As John T. Williams, an analyst at Compass Point Research & Trading, puts it, "A lot of the business lines they've added tie in very nicely with Square's original product." --Victoria Finkle