This is an "I just thought I would share post". No real reason behind it other than my love for all things trivia. I was reading the Nov-Dec 2010 issue of Mental Floss and came across this side list of pen names.
The Curious Origins of 5 Pen Names
O. Henry: As a consummate storyteller, William S. Porter had plenty of explanations for why he chose his pen name. He once told The New York Times that he took the name O. Henry from the paper's society columns to give himself some class. Other times, he attributed the moniker to his girlfriend's cat, a favorite bartender, and a guard in the prison where he served time for embezzlement.
Edward Gorey: Macabre artist Edward Gorey had plenty of alternate names: Dreary Wodge, Wardore Edgy, Dogear Wryde, Garrod Weedy, and Madame Regera Dowdy. Of course, he made it easy for his fans to spot his work; each one is an anagram of his name.
George Orwell: It's speculated that Mr. Eric Blair chose better known name because of his deep love for England. George is not only the name of the nation's patron saint, it was also the name of the king at the time, Meanwhile "Orwell" is a river that flows through Suffolk county.
J.D. Robb: Bestselling romance author Nora Roberts picked her alter ego, J.D. Robb, for very personal reasons-her sons, Jason and Dan. As for Robb, that's simply short for Roberts.
Lewis Carroll: Charles Lutwidge Dogson was an accomplished mathematician, with plenty of academic work published in his name. So when he decided to give children's writing a shot, he chose a moniker that would jeep his two identities separate-slightly. He chose Carroll for Charles and Lewis for Lutwidge.
They also have an article here that has some interesting info about different authors and books.