Here at School Street, the students gradually learn about Melvil Dewey who invented the system for where all books are shelved in the library. The 5th graders especially learn about this and may enjoy these games!
Dewey Decimal Games http://li.cusd220.lake.k12.il.us/library/DeweyDecimalGames.htm
Library Skills Game including the Dewey Decimal System http://www.ccsd.edu/bardonia/LearningGames/LibrarySkills/
"Do We" Really Know Dewey? http://library.thinkquest.org/5002/index.shtml