After playing Dark Heresy for several months, I've decided to try my hand at GMing a one-shot Dark Heresy game in a few days.

I'm looking to run a one-shot scenario that is short, and both fun for the players and easy for me to run as a newbie GM.

I would run one of the preview adventures if it wasn't for the fact that some of the players have already played through them in the current Dark Heresy campaign that is already in-progress.

So do you have any advice on which pre-written adventure I should run? Or on how to crate my own one-shot adventure?

If you're willing to spend a little money, some time and a creativity, I'd recommend the Bleeding Edge Adventures D&D modules Mansion of Shadows or Dreadful Dawn by Green Ronin. Sure, they're D&D modules but they deal heavy with investigation, intrigue and daemonic cults which fit perfectly with Dark Heresy. I've run Mansion of Shadows as a DH one shot with great success.

Sounds like an interesting possibility. I didn't want to spend too much money if I didn't have to, but that could work.

Has anybody run any of the adventures from Dark Reign? I was looking at some of them but the only ones that actually seem like they're any good also seem like they'd take several sessions to play through.

From Dark Reign I've run one Ork-based one (basic concept: Xeno-Arcanist brought Ork spores onto space station. Fails to contain it (and indeed, doesn't know how it's spreading), cue ork-on-ork-on-acolyte fights. Lots of fun, not much in terms of investigation.

I've run "Fate of the Terra Ariel" (originally Savage Worlds sci-fi adventure), a couple of homebrewed/improvised/reactive adventures, Edge of Darkness and Purge the Unclean.
Terra Ariel is a good adventure, if one adapts it to DH and makes it a part of a greater whole (I tied it with Rejoice for You Are True).

Edge of Darkness; is free and highly advisable. If the players already know it, a quick search and replace can make it all new. Lesse... Takes place on a space station.... no, better yet a starship. The alms house is an on-ship organisation who are helping several hundred people who lost their station when a chunk of the ship was shot to **** almost a year ago.
The Chiurgeon becomes a Warp Drive Enginseer, who is trying to create warp-resistant, sentient (yet entirely controllable) servitors out of the "surplus" crew. When the Enginseer realizes the Acolytes are on to him, he seals their routes out of the sections and threatens to blow the Warp Drive should they try a brute-force attack, leaving the ship stranded in the warp indefinitely.

Brutal Lament, Glass Spider and House of Ash and Dust are all quite intriguing as well. Each has plenty of opportunity for them to be changed beyond recognition from a players viewpoint, but remaining largely the same from the eyes of a GM.

After taking a look at a few scenarios from Dark Reign(many that were really bad, and a few that were incredibly good but just too **** long) I finally found Cut Off the Head.

You accompany an Inquisitor to the planet Junos to investigate a recent rise in anarchist and cultist activity. But before you can even leave your landing craft the Inquisitor is killed under mysterious circumstances.

I'll be runing it on Monday. I'll let you know how it goes.