geeks, when asked to articulate their thoughts about the series of symbols "O'REILLY", will immediately put forth one thought: animals on the front of rocking computer books. They are right, but believe it or not, O'Reilly did not start as a publishing company!
In 1978, Tim O'Reilly founded O'Reilly & Associates, which functioned at first as a technical writing consulting company. The first twinkle of the star that was to become the O'Reilly Publishing Press shined in 1984, when the company retained the rights to the manuals they were creating for Unix vendors. The fruit of their labor paid off one year later, when a drop in demand prompted the company to publish their materials as independent books.
These first books were what are now called Nutshell books - very short quasi-pamphlets that detail the basics of a subject. As demand fluctuated, O'Reilly continued to publish books, but viewed it as a backup plan for consulting. However, in January of 1988, the popularity of their Xlib manuals showed that there was a huge market for the books that O'Reilly was and would be churning out, and so publishing transformed into the core of O'Reilly's business.
As more and more people made requests to O'Reilly for online versions of some of their more popular books, O'Reilly began to realize that the many standards for online books was non-optimal: it would be difficult to maintain four different versions of all their books, and so, in 1991, O'Reilly teamed up with DEC, Silicon Graphics, and Hal Computer Systems to produce DocBook, which has become a de facto standard.
Their first online book (The Whole Internet User's Guide and Catalog (remember, this was about 1990)) proved to be a major success. This would pave the way for many other web sites to be later run by O'Reilly: perl.com, xml.com, oreilly.com, oreillynet.com, and others. These websites offer tips for developers, excerpts from books, code snippets, and more.
Today, O'Reilly publishes more than 405 books, with more being churned out by the day. Hundreds more are out of print, but still available used. New books range in price from $8 (http://www.oreilly.com/catalog/smileys/) to $500. (Yes, five hundred USD. http://www.oreilly.com/catalog/p2presearch/) Most of their books focus on programming issues, but some deal with other things: protocols, paradigms, applications. All are computer-related. O'Reilly is in a rather unique situation as a publisher of computer books, for they started as computer people, rather than book people. Their books are both usable and easy-to-read, and when you buy an O'Reilly book, you know that it has been written by a true guru in their field.
Edie Freedman, O'Reilly's Creative Director, has been designing the distinctive animal covers for O'Reilly since the 1980's. Being of a non-Unix background, she found terms such as sed and awk exotic. One day she came across a collection of 18th and 19th century engravings featuring animals, and immediately associated sed and awk with a pair of lorises (http://www.oreilly.com/catalog/sed2/). Thus a legend was born.
Now, dedicated graphic artists, such as Lori Houston, work to get animals into very specific poses for books. Normally a book designer, or sometimes the author, will approach Lori with an idea, but sometimes she suggests her own.
The choice of animals is sometimes revealed, but usually not. For GNU Emacs, a gnu was featured. For perl, a camel waits on the cover. The camel can be said to have common attributes with perl: capable of great feats of strength, hardy, viewed as somewhat dirty by corporate suits... A collection of incredibly ugly toads adorn the cover of Windows Annoyances books.
Other choices require more thought. The book Web Caching has a rock thrush on the cover. The bird looks fast and agile, but also frail. Similarly, web caching - done properly - can make your web sites load faster, render more smoothly, and consume less bandwidth. Done improperly, it can have disastrous results. Unfortunately, things get more and more obscure from there. What relation does a crab have to TCP/IP? I can't venture a guess.