They're briefly mentioned in The Buried Age, but not really featured. I'm not aware of anything else.
Weren't they mentioned in KRAD's Demons Of Air And Darkness aswell? Nog got some sort of shield modification from them I think.
I can't remember if the are visited in "Imbalance" (TNG #22, 1992)or if that's that other insectoid race that was heard off screen in "The Big Goodbye".
I think I asked this same question a year or so ago. I was hoping there was some books with the Sheliak in them, as I always thought they would have made a good recurring villain on the show. But alas, they never returned, on the show or in the lit.
Maybe, with a bit of luck, they might reappear in a Typhon Pact novel. Being more than a single-planet-power, they could have bearing on the astropolitical scale.
http://memory-beta.wikia.com/wiki/Sheliak_Corporate http://memory-beta.wikia.com/wiki/Sheliak_(mirror)
The Sheliak Corporate seems to be quite a ways away from the central UFP, so I'm guessing that has some part in their lack of presence. Still, it would be great to see them show up sometime.In a Titan or Aventine book, maybe? I can definitely see them getting along with the Typhon Pact, especially the Tholians, given their similar senses of exactitude. Might be interesting if the Federation reached out to the Sheliak first, though...
Oh, another thought... have they shown up in any Trek comics? Maybe during MJF's run on DC's TNG series?
Someone forgot he mentioned them in DTI: Watching the clock. Edit - I see Freman already saw this particular slip.
No, I don't remember them ever appearing. By the way, it may be worth noting that Sheliak is the Arabic name for Beta Lyrae, the semidetached binary star that was featured in TAS: "The Slaver Weapon" (and of course "The Soft Weapon," the Known Space novella it was based on). Although "The Slaver Weapon" portrayed it as an uninhabited system, and of course there's no way such a turbulent, short-lived binary supergiant could support life. Perhaps the Sheliak are called that by the Federation because they hail from the sector of space that contains Beta Lyrae.
Which is exactly where Geoffrey Mandel placed them in Star Charts. You can see it on the giant fold-out map at the back, in the "Known Space" inset. A good long ways away from the main body of the UFP.