From the Washington Post :
I, Rigoberta Menchú: An Indian Woman in Guatemala , a 1984 memoir by a Nobel Prize-winner, is found to recount incidents that she could not have witnessed.
J.T. LeRoy, supposedly a male teenage hustler and the author of Sarah and The Heart is Deceitful Above All Things , is revealed as the fictional creation of Laura Albert and her husband, Geoffrey Knoop.
Jihad by Tom Carew. In which the author recounted his exploits with the SAS and his time training Afghan rebels. While Carew served in the army, he was providing support to--not actually in--the SAS (although he was SAS trained).
The Cage by Thomas Abraham. Having fought in the Vietnam War, Abraham told how the Viet Cong held him as a PoW. His claims of capture and subsequent escape were disputed by fellow veterans and remained unsubstantiated by military records.
Widower's House by John Bayley. An account of life after the death of his wife Iris Murdoch included the portrayal of two women who chased after him. He later admitted that they were actually composite characters, 'both real and unreal.'
So even a respected literary type like John Bayley (ex-Warton Professor of English at Oxford) mixes a little fiction into his fact!
Roots by Alex Haley. A chronicle of seven generations of Haley's family was awarded the Pulitzer Prize. Many of his genealogical claims were shown to be falsified, and he reached an out of court settlement for plagiarism with Harold Courlander, author of The African.