- Official Report of the Niger Valley Exploring PartyAuthor: Martin Robison DelanyReleased on Project Gutenberg: July 22, 2007
- Official views of the World's Columbian ExpositionAuthor: C. D. (Charles Dudley) Arnold, Higinbotham, H. D.Released on Project Gutenberg: October 2, 2007
- Oh Little Town of BethlehemAuthor: Lewis Redner, Davis, Rick [Arranger]Released on Project Gutenberg: June 17, 2006
- Oh! Susannah!: A Farcical Comedy in Three ActsAuthor: Mark AmbientReleased on Project Gutenberg: June 12, 2007
- Oh, Money! Money! A NovelAuthor: Eleanor H. (Eleanor Hodgman) PorterReleased on Project Gutenberg: June 1, 2004
- Oh, You Tex!Author: William MacLeod RaineReleased on Project Gutenberg: August 15, 2007
- Ohio Arbor Day 1913: Arbor and Bird Day Manual: Issued for the Benefit of the Schools of our StateAuthor: Clifton, Grace R. [Compiler]Released on Project Gutenberg: October 13, 2007
- Ohio Biological Survey, Bull. 10, Vol. 11, No. 6: The Ascomycetes of Ohio IV and VAuthor: Bruce Fink, Leafy Jane Corrington HilkerReleased on Project Gutenberg: July 4, 2006
- Okewood of the Secret ServiceAuthor: Valentine WilliamsReleased on Project Gutenberg: December 1, 2000
- Oklahoma and Other PoemsAuthor: Freeman Edwin MillerReleased on Project Gutenberg: February 7, 2005
- Olaf the Glorious: A Story of the Viking AgeAuthor: Robert LeightonReleased on Project Gutenberg: December 1, 2005
- Old and New MastersAuthor: Robert LyndReleased on Project Gutenberg: June 1, 2004
- Old BalladsAuthor: VariousReleased on Project Gutenberg: February 1, 2004
- Old CalabriaAuthor: Norman DouglasReleased on Project Gutenberg: January 1, 2005
- Old Caravan DaysAuthor: Mary Hartwell CatherwoodReleased on Project Gutenberg: November 1, 2004
- Old ChristmasAuthor: Washington IrvingReleased on Project Gutenberg: May 14, 2006
- Old Christmas: from the Sketch Book of Washington IrvingAuthor: Washington Irving, Randolph CaldecottReleased on Project Gutenberg: February 24, 2007
- Old Cookery Books and Ancient CuisineAuthor: William Carew HazlittReleased on Project Gutenberg: May 1, 2004
- Old Creole Days: A Story of Creole LifeAuthor: George Washington CableReleased on Project Gutenberg: November 1, 2003
- Old DanielAuthor: Hodson, ThomasReleased on Project Gutenberg: October 20, 2007
- Old EbenezerAuthor: Opie Percival ReadReleased on Project Gutenberg: October 27, 2007
- Old English librariesAuthor: Ernest Albert Savage, James HuttReleased on Project Gutenberg: January 1, 1999
- Old English Sports, Pastimes and CustomsAuthor: P. H. (Peter Hampson) DitchfieldReleased on Project Gutenberg: December 10, 2004
- Old Fires and Profitable Ghosts: A Book of StoriesAuthor: Arthur Quiller-CouchReleased on Project Gutenberg: October 19, 2004
- Old Fogy: His Musical Opinions and GrotesquesAuthor: James HunekerReleased on Project Gutenberg: December 19, 2006
- Old Fort Snelling, 1819-1858Author: Marcus Lee HansenReleased on Project Gutenberg: September 22, 2007
- Old French Romances, Done into EnglishAuthor: William Morris, Joseph JacobsReleased on Project Gutenberg: June 1, 2004
- Old Friends: Essays in Epistolary ParodyAuthor: Andrew LangReleased on Project Gutenberg: December 1, 1999
- Old Fritz and the New EraAuthor: L. (Luise) Mühlbach, Langley, Peter [Translator]Released on Project Gutenberg: October 1, 2002
- Old Gold: The Cruise of the "Jason" BrigAuthor: George Manville Fenn, Stanley L. WoodReleased on Project Gutenberg: May 8, 2007
- Old Gorgon Graham: More Letters from a Self-Made Merchant to His SonAuthor: George Horace LorimerReleased on Project Gutenberg: April 1, 2004
- Old Granny FoxAuthor: Thornton W. (Thornton Waldo) BurgessReleased on Project Gutenberg: January 1, 2004
- Old Greek Folk Stories Told AnewAuthor: Josephine Preston PeabodyReleased on Project Gutenberg: November 1, 2005
- Old Greek StoriesAuthor: James BaldwinReleased on Project Gutenberg: March 1, 2004
- Old Indian DaysAuthor: Charles A. EastmanReleased on Project Gutenberg: July 5, 2008
- Old Indian LegendsAuthor: Zitkala-SaReleased on Project Gutenberg: July 5, 2008
- Old Jabe's Marital Experiments: 1908Author: Thomas Nelson PageReleased on Project Gutenberg: November 16, 2007
- Old JackAuthor: William Henry Giles KingstonReleased on Project Gutenberg: October 17, 2007
- Old John Brown, the man whose soul is marching onAuthor: Hawkins, WalterReleased on Project Gutenberg: January 1, 2000
- Old JunkAuthor: H. M. (Henry Major) Tomlinson, S. K. (Samuel Kerkham) RatcliffeReleased on Project Gutenberg: May 19, 2008
- Old KaskaskiaAuthor: Mary Hartwell CatherwoodReleased on Project Gutenberg: May 19, 2006
- Old Lady Mary: A Story of the Seen and the UnseenAuthor: Mrs. (Margaret) OliphantReleased on Project Gutenberg: November 1, 2003
- Old Lady Number 31Author: Louise ForsslundReleased on Project Gutenberg: November 1, 2003
- Old Love Stories RetoldAuthor: Richard Le GallienneReleased on Project Gutenberg: June 1, 2002
- Old Mackinaw; Or, The Fortress of the Lakes and its SurroundingsAuthor: W. P. (William Peter) StricklandReleased on Project Gutenberg: September 9, 2007
- Old Man Savarin, and Other StoriesAuthor: Edward William ThomsonReleased on Project Gutenberg: January 12, 2007
- Old Mission Stories of CaliforniaAuthor: Charles Franklin CarterReleased on Project Gutenberg: September 1, 2004
- Old Mortality, CompleteAuthor: Walter ScottReleased on Project Gutenberg: August 22, 2004
- Old Mortality, Volume 1.Author: Walter ScottReleased on Project Gutenberg: August 22, 2004
- Old Mortality, Volume 2.Author: Walter ScottReleased on Project Gutenberg: August 22, 2004
- Old Mother Hubbard and Her DogAuthor: UnknownReleased on Project Gutenberg: November 6, 2007
- Old Mother West WindAuthor: Thornton W. (Thornton Waldo) BurgessReleased on Project Gutenberg: March 1, 2001
- Old Mr. WileyAuthor: Greye La SpinaReleased on Project Gutenberg: November 6, 2007
- Old News: (From: "The Snow Image and Other Twice-Told Tales")Author: Nathaniel HawthorneReleased on Project Gutenberg: November 1, 2005
- Old Peter's Russian TalesAuthor: Arthur Ransome, Dmitrii Isidorovich MitrokhinReleased on Project Gutenberg: November 2, 2005
- Old Portraits and Modern Sketches: Part 1 from Volume VI of The Works of John Greenleaf WhittierAuthor: John Greenleaf WhittierReleased on Project Gutenberg: December 1, 2005
- Old Rail Fence Corners: The A. B. C's. of Minnesota HistoryAuthor: Lucy Leavenworth Wilder MorrisReleased on Project Gutenberg: July 30, 2007
- Old Rose and SilverAuthor: Myrtle ReedReleased on Project Gutenberg: April 1, 2004
- Old Saint Paul's: A Tale of the Plague and the FireAuthor: William Harrison AinsworthReleased on Project Gutenberg: February 1, 2004
- Old Scores and New Readings: Discussions on Music & Certain MusiciansAuthor: John F. RuncimanReleased on Project Gutenberg: March 15, 2005