"In Sir Arthur Conon Doyle's tales, Sherlock Holmes kept a large and sprawling commonplace book upon his shelves, essentially his own home-grown encyclopedia of people, places, crimes, and pertinent facts, like the colour of mud from various locations, or the consistency of tobacco ashes. In the middle of a case, Holmes would rush to his commonplace, haul down a book, and read out a newspaper article concerning (say) the disappearance of a hydraulics engineer a year prior. His attic of a brain remembered vague references, but the books held the details that allowed him to pursue his work."
EDIT: and since I'm on it, those who use Tomboy in that capacity will be probably happy to hear that Tomdroid[1] — a Tomboy client for Android with synchronization through Ubuntu One — finally can not only view notes but also edit them and sync back. Not the version from the Play Store yet but the beta with all the new features is available as .apk from their Launchpad website.
From http://www.diyplanner.com/docs/commonplace1:
"In Sir Arthur Conon Doyle's tales, Sherlock Holmes kept a large and sprawling commonplace book upon his shelves, essentially his own home-grown encyclopedia of people, places, crimes, and pertinent facts, like the colour of mud from various locations, or the consistency of tobacco ashes. In the middle of a case, Holmes would rush to his commonplace, haul down a book, and read out a newspaper article concerning (say) the disappearance of a hydraulics engineer a year prior. His attic of a brain remembered vague references, but the books held the details that allowed him to pursue his work."