PJ Farmer wrote one Doc Savage adventure: Escape From Loki.

A mini-biography by Duane Spurlock

William G. Bogart ghosted fourteen Doc Savage novels. He's also known among Doc fandom for The Crazy Indian, a short novel originally written as Doc Savage adventure; however, when Bogart lost his spot as a Robeson, he rewrote this story as a stand-alone novel about a group called The Adventurers. Essentially, Bogart only changed the names, although in at least one spot a character is called "Monk." Oops.

Tom Johnson's Fading Shadows press reprinted The Crazy Indian in Action Adventure Stories # 17, but that issue is now out of print, according to the Fading Shadows web site.

Bogart was a prolific writer of short stories for the pulps. Many were used as backup stories to fill out issues of Doc Savage, The Shadow, and The Avenger. A quick search on the Advanced Book Exchange turns up these magazine entries for Bogart, which is by no means complete, but gives you an idea of the sort of places his work showed up:

-Backup stories in these issues of The Shadow: March 15, 1937; November 1, 1940; January 1945; February 1944; and November 1944.
-Stories in the Canadian edition of Detective Story Magazine: April 1943; February 1944; and June 1944.
-A story in the June 10, 1943, issue of Short Stories magazine.

Dave Kalb's great site, The Avenger Archives, offers all the backup stories that ran in each issue of The Avenger. Included are the two stories by Bogart that ran in that magazine: "Killer 'Round The Bend," which appeared in the October 1939 issue, and "Skeleton In Our Closet," which appeared in the February 1940 issue.

By the way, you can find a photo of Bogart at Rob Smalley's fun site, Doc Savage, The Supreme Adventurer.

Like many pulpsters, Bogart tried to build a writing career outside of the pulp magazines. He wrote a number of mystery novels, most featuring a private eye named Johnny Saxon. It is for Johnny Saxon that fans of hard-boiled writing remember Bogart, but even in that arena, he is a minor figure. Here is at least a partial listing of his novels:

Hell On Friday (the description I found for this one makes it sound interesting to pulp fans: "Johnny Saxon, the protagonist of this scarce hard-boiled novel, is a former pulp writer turned detective, and much of the murder mystery revolves in and around the world of pulp magazine publishing")
Johnny Saxon (for which I found this description: "private investigator and former mystery writer Johnny Saxon is hired to help a woman regain her memory, only to discover that the woman herself is probably the next target of a killer")
Murder Is Forgetful, Murder Man, The Queen City Murder Case, and Singapore (a movie tie-in of the film starring Ava Gardner and Fred MacMurray)

I also located on ABE a novel by William Bogart titled Sands Street, but I'm not sure that it is by the same William Bogart. However, it was published by the same New York company that released Hell on Friday-- Jonathan Swift -- so there's reason to suppose that the book was indeed written by the same man. Hell on Friday was published in hardback in 1941. Sands Street was published in hardback in 1942. A seller on ABE described Sands Street in this rather terse fashion: "The meeting place of the men who follow the sea and the women who follow the men."

Evelyn Coulson wrote one Doc Savage novel.

Harold Davis wrote 13 Doc Savage novels.

Laurence Donovan (alias Norman Danberg) wrote nine Doc Savage novels.

Alan Hathway wrote four Doc Savage novels.

Ryerson Johnson wrote three Doc Savage novels.

Will Murray wrote seven Doc Savage novels. He announced another six novels:

The Infernal Buddah, The Phantom Lagoon, The War-Maker, The Yesterday Man (renamed: The Ice Genius), The Smoking Specter, The Nullifier