Who knew $1-a-night DVDs would take off in such a big way? Coinstar, apparently. Its Redbox subsidiary started humbly enough as an experiment in 2004 but is now one of the company's biggest moneymakers. Operating income increased nearly 47% last year on sales of $1.8 billion, largely driven by the 35,400 DVD kiosks in supermarkets, pharmacies, and convenience stores around the country. Later this year, Redbox will grow further thanks to the $100 million acquisition of NCR Corp.'s entertainment business, the unit behind the Blockbuster Express brand, and a new streaming service in partnership with Verizon, due out the second half of this year.