- Orpheus in Mayfair, and Other Stories and SketchesAuthor: Maurice BaringReleased on Project Gutenberg: April 4, 2006
- Orrain: A RomanceAuthor: Levett Yeats, S. (Sidney)Released on Project Gutenberg: December 26, 2006
- OrthodoxyAuthor: G. K. (Gilbert Keith) ChestertonReleased on Project Gutenberg: May 1, 1994
- OrthodoxyAuthor: G. K. (Gilbert Keith) ChestertonReleased on Project Gutenberg: September 28, 2005
- OrthographyAuthor: Elmer W. (Elmer Warren) Cavins, Edwin C. (Edwin Crawford) HewettReleased on Project Gutenberg: November 7, 2007
- Osage TraditionsAuthor: James Owen DorseyReleased on Project Gutenberg: October 4, 2006
- Oscar the Detective; Or, Dudie Dunne, The Exquisite DetectiveAuthor: Old SleuthReleased on Project Gutenberg: September 19, 2006
- Oscar Wilde, His Life and Confessions — Volume 1Author: Frank HarrisReleased on Project Gutenberg: January 1, 2003
- Oscar Wilde, His Life and Confessions. Volume 1 (of 2)Author: Frank HarrisReleased on Project Gutenberg: October 17, 2005
- Oscar Wilde, His Life and Confessions. Volume 2 (of 2)Author: Frank HarrisReleased on Project Gutenberg: October 17, 2005
- Oscar; Or, The Boy Who Had His Own WayAuthor: Walter AimwellReleased on Project Gutenberg: April 11, 2006
- Oswald Langdon: or, Pierre and Paul Lanier. A Romance of 1894-1898Author: Hamilton, Levi JacksonReleased on Project Gutenberg: August 2, 2007
- OthelloAuthor: William ShakespeareReleased on Project Gutenberg: December 1, 1997
- OthelloAuthor: William ShakespeareReleased on Project Gutenberg: November 1, 1998
- OthelloAuthor: William ShakespeareReleased on Project Gutenberg: June 1, 1999
- OthelloAuthor: William ShakespeareReleased on Project Gutenberg: July 1, 2000
- Other Main-Travelled RoadsAuthor: Hamlin GarlandReleased on Project Gutenberg: March 1, 2007
- Other People's Business: The Romantic Career of the Practical Miss DaleAuthor: Harriet L. (Harriet Lummis) SmithReleased on Project Gutenberg: October 23, 2007
- Other People's MoneyAuthor: Emile GaboriauReleased on Project Gutenberg: May 1, 1999
- Other Tales and Sketches: (From: "The Doliver Romance and Other Pieces: Tales and Sketches")Author: Nathaniel HawthorneReleased on Project Gutenberg: November 1, 2005
- Other Things Being EqualAuthor: Emma WolfReleased on Project Gutenberg: August 1, 1999
- Other Worlds: Their Nature, Possibilities and Habitability in the Light of the Latest DiscoveriesAuthor: Garrett Putman ServissReleased on Project Gutenberg: May 22, 2006
- Otto of the Silver HandAuthor: Howard PyleReleased on Project Gutenberg: October 1, 2001
- Our American CousinAuthor: Tom TaylorReleased on Project Gutenberg: April 1, 2002
- Our Boys: Entertaining Stories by Popular AuthorsAuthor: VariousReleased on Project Gutenberg: July 1, 2005
- Our Casualty, and Other Stories: 1918Author: George A. BirminghamReleased on Project Gutenberg: January 21, 2008
- Our Catholic Heritage in English Literature of Pre-Conquest DaysAuthor: Emily Henrietta HickeyReleased on Project Gutenberg: October 1, 2005
- Our Changing ConstitutionAuthor: Charles W. (Charles Wheeler) PiersonReleased on Project Gutenberg: November 20, 2004
- Our Churches and Chapels: Their Parsons, Priests, & Congregations: Being a Critical and Historical Account of Every Place of Worship in PrestonAuthor: AtticusReleased on Project Gutenberg: December 1, 2003
- Our Common Insects: A Popular Account of the Insects of Our Fields, Forests, Gardens and HousesAuthor: A. S. (Alpheus Spring) PackardReleased on Project Gutenberg: January 23, 2008
- Our Day: In the Light of ProphecyAuthor: William Ambrose SpicerReleased on Project Gutenberg: June 5, 2006
- Our Deportment: Or the Manners, Conduct and Dress of the Most Refined SocietyAuthor: Young, John H.Released on Project Gutenberg: January 25, 2006
- Our Elizabeth: A Humour NovelAuthor: Florence A. (Florence Antoinette) Kilpatrick, Ernest ForbesReleased on Project Gutenberg: May 22, 2006
- Our Farm of Four Acres and the Money We Made by ItAuthor: Coulton, Miss, Peter B. MeadReleased on Project Gutenberg: March 1, 2004
- Our Fathers Have Told Us: Part I. The Bible of AmiensAuthor: John RuskinReleased on Project Gutenberg: January 26, 2008
- Our Foreigners: A Chronicle of Americans in the MakingAuthor: Samuel Peter OrthReleased on Project Gutenberg: January 28, 2005
- Our Frank: and other storiesAuthor: Amy WaltonReleased on Project Gutenberg: October 20, 2007
- Our Friend John BurroughsAuthor: Clara BarrusReleased on Project Gutenberg: September 1, 2004
- Our Friend the CharlatanAuthor: George GissingReleased on Project Gutenberg: August 1, 2003
- Our Friend the DogAuthor: Maurice Maeterlinck, Cecil Aldin, Alexander Teixeira de MattosReleased on Project Gutenberg: April 20, 2006
- Our GiftAuthor: Teachers of the School Street Universalist Sunday School. BostonReleased on Project Gutenberg: January 1, 2004
- Our Government: Local, State, and National: Idaho EditionAuthor: James Alton James, Albert Hart Sanford, James Timbrell WorltonReleased on Project Gutenberg: July 20, 2004
- Our Holidays: Their Meaning and Spirit; retold from St. NicholasAuthor: VariousReleased on Project Gutenberg: January 29, 2005
- Our Hundred Days in EuropeAuthor: Oliver Wendell HolmesReleased on Project Gutenberg: January 1, 2005
- Our Lady Saint MaryAuthor: J. G. H. (Joseph Gayle Hurd) BarryReleased on Project Gutenberg: June 1, 2004
- Our Legal Heritage : 600-1776 King Aethelbert - King George IIIAuthor: Reilly, S. A.Released on Project Gutenberg: October 1, 2004
- Our Legal Heritage, King AEthelbert, 596 to King George III, 1775Author: Reilly, S. A.Released on Project Gutenberg: September 5, 2004
- Our Legal Heritage: The First Thousand Years: 600 - 1600: King Aethelbert - Queen ElizabethAuthor: Reilly, S. A.Released on Project Gutenberg: April 1, 1999
- Our Little Korean CousinAuthor: H. Lee M. (Henry Lee Mitchell) PikeReleased on Project Gutenberg: April 1, 2004
- Our Little Lady: Six Hundred Years AgoAuthor: Emily Sarah Holt, Irwin, M. (Madelaine) [Illustrator]Released on Project Gutenberg: October 20, 2007
- Our Master: Thoughts for Salvationists about Their LordAuthor: Bramwell BoothReleased on Project Gutenberg: May 1, 2005
- Our Mr. Wrenn: The Romantic Adventures of a Gentle ManAuthor: Sinclair LewisReleased on Project Gutenberg: January 1, 2004
- Our Mutual FriendAuthor: Charles DickensReleased on Project Gutenberg: April 27, 2006
- Our Navy in the WarAuthor: Lawrence PerryReleased on Project Gutenberg: June 24, 2006
- Our Nervous Friends — Illustrating the Mastery of NervousnessAuthor: Robert S. (Robert Sproul) CarrollReleased on Project Gutenberg: June 1, 2004
- Our New Neighbors At PonkapogAuthor: Thomas Bailey AldrichReleased on Project Gutenberg: November 6, 2007
- Our Nig; Or, Sketches from the Life of a Free Black, in a Two-story White House, North: Showing That Slavery's Shadows Fall Even ThereAuthor: Harriet E. WilsonReleased on Project Gutenberg: July 1, 1996
- Our Old Home: A Series of English SketchesAuthor: Nathaniel HawthorneReleased on Project Gutenberg: May 1, 2005
- Our PetsAuthor: AnonymousReleased on Project Gutenberg: November 7, 2007
- Our Pilots in the AirAuthor: William Perry BrownReleased on Project Gutenberg: July 1, 2004