In Arabic:
Nubthah fi Fan Al-Musiqa (Music, 1905)
Ara'is al-Muruj (Nymphs of the Valley, also translated as Spirit Brides and Brides of the Prairie, 1906)
Al-Arwah al-Mutamarrida (Rebellious Spirits, 1908)
Al-Ajniha al-Mutakassira (Broken Wings (book)|Broken Wings, 1912)
Dam'a wa Ibtisama (A Tear and A Smile, 1914)
Al-Mawakib (The Processions, 1919)
Al-‘Awāsif (The Tempests, 1920)
Al-Bada'i' waal-Tara'if (The New and the Marvellous, 1923)
In English, prior to his death:
The Madman (1918)
Twenty Drawings (1919)
The Forerunner (1920)
The Prophet (book) (1923)
Sand and Foam (1926)
Kingdom of the Imagination (1927)
Jesus, The Son of Man (1928)
The Earth Gods (1931)
Posthumous, in English:
The Wanderer (1932)
The Prophet (book) | The Garden of the Prophet (1933, completed by Barbara Young)
Lazarus and his Beloved (Play, 1933)
Collections:
Prose Poems (1934)
Secrets of the Heart (1947)
A Treasury of Kahlil Gibran (1951)
A Self-Portrait (1959)
Thoughts and Meditations (1960)
A Second Treasury of Kahlil Gibran (1962)
Spiritual Sayings (1962)
Voice of the Master (1963)
Mirrors of the Soul (1965)
Between Night & Morn (1972)
A Third Treasury of Kahlil Gibran (1975)
The Storm (1994)
The Beloved (1994)
The Vision (1994)
Eye of the Prophet (1995)
The Treasured Writings of Kahlil Gibran (1995)
Other:
Beloved Prophet, The love letters of Khalil Gibran and Mary Haskell, and her private journal (1972, edited by Virginia Hilu)
Kahlil Gibran: Horizons of the Painter (Nicolas Sursock Museum, Beirut)
At the Source of the Prophet: A Search for Clues by Charlotte & Hans Munch
wortbildduo.de
Khalil-Gibran.com
ebook.de
The Art of Kahlil Gibran (Telfair Books, Savannah, Georgia)
Gibran: El Profeta (Museo Soumaya, Fundacion Carlos Slim)
Museo Soumaya (see: Publicaciones section of Museum's website)