#6 Priceline

2012 Fastest-Growing rank: 14

Previous rank: 12

CEO: Jeffery H. Boyd

Priceline was the brainchild of digital entrepreneur Jay S. Walker, founded in 1997. Priceline.com is an Internet-based transactional service that offers products in two categories: a travel service that offers leisure airline tickets, hotel rooms, rental cars, packaged vacations and cruises; and a personal finance service that markets home mortgages, refinancing and home equity loans through an independent licensee.

Net income nearly doubled to $1.05 billion last in 2011 compared with the year before. Yet again, the cause was largely international sales, which grew to 78% of the company's overall bookings and Booking.com, the Connecticut-based international hotel reservations site it bought back in 2004.

#5 3D Systems

2012 Fastest-Growing rank: 12

Previous rank: N.R.

CEO: Abe Reichental

Founded by Chuck Hull in 1986 and headquartered in Rock Hill, South Carolina, 3D Systems is a global company that develops and sells systems, materials, and software for solid imaging. Its products are meant to make manufacturing processes more efficient, without requiring tooling. 3D Systems creates product concept models, precision and functional prototypes, master patterns for tooling, as well as production parts for direct digital manufacturing.

Sales climbed 44% year-over-year to $230 million, with half those sales coming from the U.S., and profits grew to $35 million, even as the company increased spending in global research and development.