International Standard Book Numbers
Books published in the past four decades have a 13-digit code called an International Standard Book Number, or ISBN. Bowker, a company in New Providence, New Jersey, has been the sole supplier of ISBNs to U.S. publishers since the codes were adopted by the International Organization for Standardization in 1970. The original publisher of Publishers Weekly, Bowker was established by Richard Rogers Bowker in 1872. In 2001, it was acquired by Cambridge Information Group, an investment firm. Bowker charges $125 for a single ISBN and offers bulk discounts.

Electronic Catalog
Forget about card catalogs. These days, you can log on to the Boston Public Library's website to search for some 20 million items in an electronic catalog developed by Toronto-based BiblioCommons. You can check book availability at various branches, peruse reviews by readers, and download content from the catalog. Beth Jefferson and Patrick Kennedy co-founded BiblioCommons as a nonprofit youth literacy initiative in 2004 and switched to a for-profit model in 2006. The 18-employee company has set up electronic catalogs for dozens of library systems, including the public libraries in Seattle and Ottawa.

Digital Downloads
Patrons downloaded more than 13,000 e-books, audio books, songs, and videos from the Boston Public Library's website last year. Cleveland-based OverDrive supplies the digital content, along with services such as download fulfillment and digital rights management. The files, which can be downloaded to computers and a variety of mobile devices, including e-readers, iPads, iPhones, and Android smartphones, automatically disappear on their due date. CEO Steve Potash founded OverDrive in 1986. The 120-employee company now supplies digital content to more than 13,000 libraries, schools, and colleges worldwide, including the New York Public Library.

Library Cards
In 2010, more than 38,000 Boston residents signed up for new public-library cards, which were made by Ultra Plastic Printing of Akron. When members borrow material, librarians swipe the cards to update the accounts in the library's computer system. Ken Thompson started Ultra in 1992. Today, the company has 50 employees and $5 million in annual sales. It makes cards for 200 library systems throughout the country, along with ID cards, gift cards, and key cards for hotels.