In addition to his BLACK MAGIC stories for Simon&Kirby Ditko worked on the CAPTAIN 3-D comic that S&K did for Harvey, and possibly other 3-D comics of the era (possibly unpublished), working with other artists on the backgrounds (as the process of creating 3-D comics was apparently quite labour-intensive)
I don't know how much Ditko there might be in that, but look for a newly coloured 2-D reprint in one of Joe Simon's reprints of the S&K material next year.
STRANGE FANTASY #9  had the story "Hair Yee-eeee", a story that Bruce Hamilton has identified as another (like "Stretching Things") that he sold to Stanmor and they re-sold to Farrell. Some people see a degree of Ditko in the art, though almost certainly not Ditko solo (there's a mark which might be an initial "SS" on the first page). This scene, for example:
Possibly related to the above, an artist named Sy Moskowitz briefly worked in comics around the same time as Ditko broke in, doing some work for Charlton, Gilberton (Classics Illustrated) and Marvel (including a few stories with Joe Kubert). I haven't looked at too much of it, but some people see a few signs of Ditko in a few of his stories, and Greg Theakston even included "The Mark of the Ripper" from Charlton's STRANGE SUSPENSE STORIES #21  in his book STEVE DITKO: EDGE OF GENIUS . I'm not 100% convinced it belonged, but judge for yourself.
No reasonable way of knowing at this point what role Ditko might have had in some of these stories, but speculation clearly labeled as such can be fun. Any other stories from that era you see something Ditkoesque in? Feel free to comment, and include a scan or two of a likely panel or two if you can.