For a change of pace I tried to write a 1,000-word short story for each of the W40K factions. I've read all of three Horus Heresy novels and a bunch of Wiki entries and never actually played the game, so these are probably as uncanonical and wrong as you can get, but they were kind of fun to do.
Chaos: A Riddle in Three Parts
Eldar: A Time to Let Go
Imperium: A Few Questions
Necrons: BirthFail Exigency
Orks: Triumph of Technology
Orks #2: The Prisoner and the Commissar
Tyranids: Sympathy for the Hive Mind
Update July 30, 2020: I think the BT stuff has been up for long enough, several years in some cases, that interest has more or less dried up. The pages sometimes get a ping or two, but that's either bots or people who leave no comment or feedback so there's nothing in it for me, quite frankly. So I've taken all the pages down and deleted the PDF files from Dropbox.
If you're still interested in one of these stories, drop me a line (such as by leaving a comment on this page) and let me know.